Corretor Forex Três Lagoas: Par Trading System And Method

O segredo para encontrar lucros em pares Trading. Quants é o nome de Wall Street para pesquisadores de mercado que usam a análise quantitativa para desenvolver estratégias de negociação lucrativas. Em resumo, um quant pente através de relações de preços e relações matemáticas entre empresas ou veículos comerciais, a fim de divina oportunidades comerciais lucrativas Durante a década de 1980, Trabalhando para Morgan Stanley ouro golpeado com uma estratégia chamada o comércio de pares Investidores institucionais e mesas de negociação proprietárias em grandes bancos de investimento têm vindo a utilizar a técnica desde então, e muitos fizeram um lucro arrumado com a estratégia. Ele é raramente no melhor interesse de Banqueiros de investimento e gestores de fundos mútuos para compartilhar estratégias de negociação rentável com o público, de modo que o comércio de pares permaneceu um segredo dos profissionais e alguns indivíduos hábeis até o advento da internet negociação on-line abriu a tampa em tempo real informações financeiras e deu a Novice acesso a todos os tipos de estratégias de investimento Não demorou muito para o comércio de pares para atrair Ct investidores individuais e comerciantes de pequeno porte procurando hedge sua exposição de risco para os movimentos do mercado mais amplo. O que é pares Trading. Pairs negociação tem o potencial de obter lucros através de posições simples e relativamente baixo risco O mercado de pares é neutra no mercado Significando que a direção do mercado global não afeta sua vitória ou perda. O objetivo é combinar dois veículos negociando que são altamente correlacionados, negociando um longo eo outro curto quando o par da relação do preço diverge x número de desvios padrão - x é Otimizado usando dados históricos Se o par reverte para sua tendência média, um lucro é feito em uma ou ambas as posições. Exemplo Usando Stocks. Traders pode usar dados fundamentais ou técnicos para construir um estilo de negociação de pares Nosso exemplo aqui é técnico em Natureza, mas alguns comerciantes usam uma relação PE ou outros fatores fundamentais para medir a correlação ea divergência. O primeiro passo na concepção de um comércio de pares é encontrar dois estoques que são altamente correlacionados D Geralmente isso significa que as empresas estão na mesma indústria ou sub-setor, mas nem sempre Por exemplo, o índice de rastreamento de ações como o QQQQ Nasdaq 100 ou o SPY SP 500 pode oferecer pares excelentes oportunidades comerciais Dois índices que geralmente o comércio em conjunto são o SP 500 eo Dow Jones Utilities Médio Este gráfico simples preço dos dois índices demonstra a sua correlação. Para o nosso exemplo, vamos olhar para duas empresas que são altamente correlacionados GM e Ford Uma vez que ambos são fabricantes de automóveis americanos, suas ações tendem a se mover juntos. Below é um gráfico semanal da relação de preço entre Ford e GM calculado dividindo o preço das ações da Ford por preço das ações da GM s Esta relação de preço é às vezes chamado de desempenho relativo não deve ser confundido com o índice de força relativa algo completamente diferente A linha branca central Representa a razão de preço médio nos últimos dois anos. As linhas amarela e vermelha representam um e dois desvios padrão da relação média, respectivamente Y. No gráfico abaixo, o potencial de lucro pode ser identificado quando a relação de preços atinge seu primeiro ou segundo desvio. Quando essas divergências lucrativas ocorrem é hora de tomar uma posição longa no underperformer e uma posição curta no overachiever A receita de A venda a descoberto pode ajudar a cobrir o custo da posição longa, tornando o comércio de pares barato para colocar Tamanho de posição do par deve ser correspondido pelo valor do dólar em vez de número de ações desta forma um movimento 5 em um é igual a um movimento 5 no Outros Como com todos os investimentos, há um risco que os comércios poderiam mover-se no vermelho, assim que é importante determinar o optimized stop-loss pontos antes de executar o comércio de pares. Mas também com moedas, commodities e até opções No mercado de futuros mini contratos - contratos de menor porte que representam uma fração do valor da posição de tamanho normal - permitem que investidores menores Para negociar em futuros. Um comércio de pares no mercado de futuros pode envolver uma arbitragem entre o contrato de futuros e a posição de caixa de um determinado índice Quando o contrato de futuros fica à frente da posição de caixa, um comerciante pode tentar lucrar por curto - Muitas vezes, os movimentos entre um índice ou commodity e seu contrato de futuros são tão apertados que os lucros são deixados apenas para o mais rápido dos comerciantes - muitas vezes usando computadores para executar automaticamente posições enormes Em um piscar de olhos. Um exemplo Usando Options. Option comerciantes usam chamadas e puts para cobrir riscos e explorar a volatilidade ou a falta de uma chamada é um compromisso do escritor para vender ações de uma ação a um determinado preço em algum momento no futuro Um put é um compromisso do escritor para comprar ações em um determinado preço em algum momento no futuro Um par de negociação no mercado de opções pode envolver a escrever uma chamada para uma segurança que está outperforming sua pa Uma outra segurança altamente correlacionada, e combinando a posição escrevendo um put para o par a segurança underperforming Como as duas posições subjacentes reverter a sua média novamente, as opções tornam-se inútil permitindo que o comerciante bolso os rendimentos de uma ou ambas as posições. Evidence of Profitability. Em junho de 1998, a Yale School of Management publicou um artigo escrito por Even G Gatev, William Goetzmann e K Geert Rouwenhorst, que tentou provar que a negociação de pares é rentável usando dados de 1967 a 1997, o trio descobriu que mais de Um período de negociação de seis meses, o comércio de pares em média um retorno 12 Para distinguir os resultados rentáveis de sorte simples, o seu teste incluiu estimativas conservadoras de custos de transação e pares selecionados aleatoriamente Você pode encontrar o documento completo de 34 páginas here. Thes interessados nos pares Negociação técnica pode encontrar mais informações e instrução em Ganapathy Vidyamurthy s livro Pairs Trading Métodos Quantitativos e Análise que você pode encontrá-la O mercado amplo está cheio de altos e baixos que forçam os jogadores fracos e confundem até mesmo os prognosticadores mais espertos. Felizmente, usando estratégias neutras como o comércio de pares, os investidores e os comerciantes podem encontrar lucros em todas as condições do mercado A beleza do comércio de pares É a sua simplicidade O relacionamento longo e curto de dois títulos correlacionados atua como um lastro para um portfólio capturado nas águas agitadas do mercado global Boa sorte com a sua caça para o lucro em pares de negociação, e aqui s para o seu sucesso nos mercados. O máximo Quantidade de dinheiro que os Estados Unidos podem emprestar O teto da dívida foi criado sob a Segunda Liberty Bond Act. A taxa de juros em que uma instituição depositária empresta fundos mantidos no Federal Reserve para outra instituição depositária.1 Uma medida estatística da dispersão dos retornos para Um determinado índice de segurança ou de mercado A volatilidade pode ser medida. Um ato que o Congresso dos EUA aprovou em 1933 como a Lei Bancária, que proibia b comercial Ank de participar no investment. Nonfarm folha de pagamento refere-se a qualquer trabalho fora de fazendas, casas particulares e do setor sem fins lucrativos O US Bureau of Labor. The abreviatura de moeda ou símbolo de moeda para a rupia indiana INR, a moeda da Índia A rupia é composta De 1.Se proporciona um método para cumprir uma solicitação de comércio de pares e inclui os passos de receber uma pluralidade de pedidos de troca de pares que executam uma transacção para uma primeira porção de uma da pluralidade de pedidos de troca de pares e que correspondem a uma segunda porção da de A pluralidade de pedidos de troca de pares contra outra da pluralidade de pedidos de troca de pares. 46.1 Processo implementado por computador para satisfazer uma solicitação de comércio em pares, compreendendo os passos de: receber uma pluralidade de pedidos de comércio em pares, compreendendo um pedido de comércio em pares e outro pedido de comércio em pares, em que cada pedido de comércio em pares compreende uma solicitação para negociar uma primeira garantia, Um pedido para transaccionar uma segunda segurança e um pedido para transaccionar a referida primeira segurança e a referida segunda segurança com um limite mínimo de propagação, e em que a referida primeira segurança e a segunda segurança cada uma tem um preço de oferta e um preço de pedido. No mercado da dita primeira segurança e da dita segunda segurança. determinar a propagação de pedido no mercado da dita primeira segurança e da dita segunda segurança. determinar que o limite mínimo de propagação de cada pedido de comércio de pares é atingido por uma gama da dita oferta de lances E o referido pedido perguntar. Executar uma transacção entre uma primeira porção do comércio da dita primeira garantia no referido pedido de comércio de um par e pelo menos um pedido de comércio sem par, provid De que o limite mínimo de propagação da referida solicitação de comércio de um par é atingido pela referida gama do referido spread de oferta de oferta e da referida propagação de pedido de pedido e. comparação, utilizando um computador, de uma segunda porção da referida transacção da referida primeira garantia no referido comércio de um par Pedido e pelo menos uma primeira porção do comércio da referida segunda segurança na referida solicitação de comércio de um par contra a referida outra solicitação de comércio de pares, desde que uma gama do limite mínimo de propagação da referida solicitação de comércio de um par ea referida outra solicitação de comércio de pares se sobreponha com O referido intervalo do referido spread de oferta de compra e do referido spread de pedido de pedido.2 Método de acordo com a reivindicação 1, em que o passo de executar uma transacção para a referida primeira parte do comércio da referida primeira segurança na referida solicitação de negociação de um par inclui o passo de: Transacção para a dita primeira porção do comércio da dita primeira garantia na dita solicitação de comércio de um par num mercado externo.3 O método da reivindicação 1, em que o passo de executar uma transacção é executado por uma instituição financeira h O envio de um inventário de ordens e o passo de executar uma transacção inclui o passo de: executar uma transacção para a referida primeira parte do comércio da referida primeira segurança na referida solicitação de comércio de um par contra o referido inventário de ordens. Executar uma transacção entre uma segunda porção do comércio da referida segunda segurança na referida solicitação de comércio de um par e pelo menos outra solicitação de comércio de não par, desde que o limite mínimo de propagação da referida solicitação de comércio de um par seja atingido pela referida gama da referida oferta Em que o passo de executar a dita primeira porção do dito pedido de comércio de um par e executar a dita segunda porção do dito pedido de comércio de um par inclui os passos de: determinar se o preço de oferta do primeiro título e do Preço de licitação da segunda segurança satisfazer um limite de spread. determinar uma quantidade da segunda segurança que pode ser vendida com base em um tamanho de lance associado com a segunda security. calculating um equiva A quantia emprestada da referida primeira garantia que pode ser comprada com base na quantidade da referida segunda garantia que pode ser vendida. ajustar a referida quantidade equivalente da referida primeira garantia com base em critérios de ajustamento. calcular um preço de compra para a referida quantidade equivalente ajustada da referida primeira base de segurança No limite de propagação. executar uma ordem iniciadora para comprar a dita quantidade equivalente ajustada da dita primeira garantia ao dito preço de compra eexecutar uma ordem de cobertura para vender a dita quantidade da segunda garantia.5 Método de acordo com a reivindicação 4, em que o passo de executar uma Abrangendo a ordem de venda inclui o passo de executar uma ordem de cobertura para vender a referida quantidade da segunda garantia ao preço de oferta da segunda caução.6 O método da reivindicação 4 compreendendo ainda as etapas de: determinar se o preço de venda da primeira A segurança e o preço de venda do segundo seguro satisfazem um limite de spread. determinar um montante da primeira garantia que pode ser comprada com base num tamanho de oferta associado ao primeiro se Cálculo. calcular uma quantidade equivalente da referida segunda garantia que pode ser vendida com base na quantidade da segunda garantia que pode ser comprada. ajustar a referida quantidade equivalente da referida segunda garantia com base em critérios de ajustamento. calcular um preço de venda para a referida quantidade equivalente ajustada de A referida segunda garantia com base no limite de propagação. Executando uma ordem iniciadora para vender a referida quantidade equivalente ajustada da referida segunda garantia ao referido preço de venda e. executando uma ordem de cobertura para adquirir a referida quantidade da primeira garantia. 7. Método de acordo com a reivindicação 6, O passo de executar uma ordem de cobertura para compra inclui o passo de executar uma ordem de cobertura para adquirir a referida quantidade da primeira garantia ao preço de pedido da primeira garantia. 8. O método da reivindicação 6, em que os referidos critérios de ajustamento incluem uma quantidade mínima e uma Quantidade máxima.9 Método de acordo com a reivindicação 8, em que o passo de executar uma ordem de iniciação inclui o passo de: rodear a referida ordem de iniciação para um tamanho de lote redondo. O método da reivindicação 1 em que o passo de executar uma primeira porção do comércio da referida primeira segurança na referida solicitação de comércio de um par inclui o passo de executar uma primeira porção do comércio da referida primeira segurança na referida solicitação de comércio de um par Em uma pluralidade de tranches.11 Processo de acordo com a reivindicação 1, em que a referida solicitação de troca de um par tem um primeiro limite de propagação e a referida outra solicitação de troca de pares tem um segundo limite de dispersão e em que a referida etapa de coincidir com a referida segunda parte da referida transacção da referida primeira No referido pedido de comércio de um par e pelo menos uma primeira porção do comércio da referida segunda segurança no referido pedido de comércio de um par contra o referido outro pedido de comércio de pares inclui ainda os passos de: determinar que um intervalo do referido primeiro limite de propagação e do referido segundo spread Limitar as sobreposições com uma propagação do mercado. definir um nível de propagação. calcular os preços para a primeira segurança e a segunda segurança que estão dentro da propagação do mercado e com base no referido nível de spread e. Segunda porção do referido comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos uma primeira parte da transacção da referida segunda segurança na referida solicitação de comércio de um par contra a referida outra solicitação de comércio de pares com base nos referidos preços calculados.12 O método de Reivindicação 11, em que o passo de fixação de um nível de espalhamento inclui os passos de: calcular uma média entre o referido primeiro limite de propagação e o referido segundo limite de propagação e. definir o referido nível de propagação como o referido meio se a referida média estiver dentro da referida propagação de mercado.13 O método de Reivindicação 12 incluindo ainda o passo de: identificar uma quantidade de spread que está mais próxima da referida média e dentro da referida margem de mercado e. definir o referido nível de spread como a referida quantidade de spread se a referida média não estiver dentro da referida margem de mercado.14 O método da reivindicação 1 em que O referido pedido de troca de um par tem um primeiro limite de propagação, um rácio de compra e um rácio de venda, dito outro pedido de comércio de pares tem um segundo limite de propagação, um rácio de compra e um rácio de venda e em que o passo de combinar um segundo porto Ião do referido comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos a referida primeira parte da transacção da referida segunda segurança na referida solicitação de comércio de um par contra a referida outra solicitação de comércio de pares inclui ainda os passos de: determinar que a referida relação de compra E a referida relação de venda associada à referida solicitação de comércio não é igual à referida relação de compra e à referida relação de venda da referida outra solicitação de comércio de pares e que existe uma sobreposição entre a gama do referido primeiro limite de propagação e o referido segundo limite de propagação e uma propagação de mercado. Que existem preços de mercado que estão dentro da sobreposição. determinar uma quantidade de desfasamento na referida segunda segurança com base numa diferença entre a referida relação de compra e a referida relação de venda associada à referida solicitação de comércio de um par e a referida relação de compra e a referida taxa de venda do referido outro comércio de par Pedido. calcular uma quantidade cruzada para a referida primeira segurança e para a segunda segurança. seleccionar um preço de passagem para a referida primeira segurança e a segunda segurança que é Dentro da dita sobreposiï¿½o; a determinaï¿½o de que a referida quantidade de desfasamento estï¿½disponï¿½el ao dito preço de cruzamento para a dita segunda seguranï¿½; a correspondente segunda porï¿½o da dita transacï¿½o da dita primeira seguranï¿½ na dita solicitaï¿½o de um par de transacï¿½o e pelo menos a dita primeira porï¿½o da transacï¿½o da dita segunda seguranï¿½ Na referida solicitação de comércio de um par contra a referida outra solicitação de comércio de pares com base nos referidos preços seleccionados e. execução de uma transacção para a referida quantidade de desadaptação da referida segunda segurança ao referido preço de cruzamento para a referida segunda segurança.15 Método de acordo com a reivindicação 14, Que a referida quantidade de desadaptação está disponível no referido preço de cruzamento para a referida segunda segurança inclui o passo de: determinar que a referida quantidade de desadaptação está disponível num mercado externo ao referido preço de cruzamento para a referida segunda segurança. 16. Método de acordo com a reivindicação 14, Que a referida quantidade de incompatibilidade está disponível é executada por uma instituição financeira que tem um inventário de ordem e o passo de determinar que a referida A quantidade de incompatibilidade está disponível no referido preço de cruzamento para a referida segunda segurança inclui o passo de: a determinação de que a referida quantidade de desadaptação está disponível no referido inventário de ordens ao referido preço de cruzamento para a referida segunda segurança.17 O método da reivindicação 1, O referido outro pedido de comércio de pares indica um número de spreads e em que o passo de combinar uma segunda porção do referido comércio da referida primeira segurança no referido pedido de comércio de um par e pelo menos a referida primeira porção do comércio da referida segunda segurança no referido comércio de um par Solicitação contra o referido outro pedido de comércio de pares, inclui o passo de comparar uma segunda porção do referido comércio da referida primeira segurança no referido pedido de comércio de um par e pelo menos a referida primeira porção do comércio da referida segunda segurança no referido pedido de comércio de um par contra O referido outro pedido de troca de pares se o referido número de spreads é maior do que um número mínimo de spreads.18 O método da reivindicação 1 incluindo o passo de: receber uma preferência Para preencher pelo menos alguma da referida pluralidade de pedidos comerciais através do referido passo de execução. 19. Método da reivindicação 1, incluindo o passo de: receber uma preferência pelo preenchimento de pelo menos uma parte da referida pluralidade de pedidos comerciais através do referido passo de correspondência. Reivindicação 1, em que um cliente submete uma consulta relativa a um estado da referida solicitação de troca de pares e o estado da referida solicitação de troca de pares é actualizado continuamente em tempo real.21 O método da reivindicação 19 em que a referida preferência é submetida por um cliente electronicamente.22 O método De acordo com a reivindicação 1, em que um cliente recebe um relatório simultâneo quando a referida solicitação de comércio de pares é preenchida e o cliente confirma o referido comércio em par eletronicamente.23 O método da reivindicação 1 compreendendo ainda: executar uma transacção entre uma segunda porção do comércio da referida segunda segurança em A referida solicitação de comércio de um par e pelo menos outra solicitação de comércio de não par, desde que o limite mínimo de propagação da referida solicitação de comércio de um par seja atingido pela referida gama da referida oferta de licitação D e o dito pedido de pedido de pedido, e em que o passo de executar a dita primeira porção do dito pedido de troca de um par e executar a dita segunda porção do dito pedido de troca de um par inclui o passo de determinar se o preço de pedido do primeiro Preço da segunda segurança satisfazer um limite de propagação. determinar uma quantidade da segunda segurança que pode ser comprada com base num tamanho de pedido associado à segunda segurança. calcular um montante equivalente da referida primeira garantia que pode ser vendida com base na quantidade da Segunda segurança que pode ser comprada. ajustar a dita quantidade equivalente da dita primeira garantia com base em critérios de ajustamento. calcular um preço de venda para a dita quantidade equivalente ajustada da dita primeira garantia com base no limite de spread. executar uma ordem de início para vender a dita quantidade equivalente ajustada de A referida primeira segurança ao referido preço de venda e. execução de uma ordem de cobertura para adquirir a referida quantidade da referida segunda segurança.24 Um sistema para cumprir um par trad Em que cada solicitação de comércio de pares compreende uma solicitação para trocar uma primeira garantia, uma solicitação para negociar uma segunda segurança e uma solicitação para O comércio disse a primeira segurança e a segunda segurança com um limite mínimo de propagação, e em que a referida primeira segurança e a segunda segurança cada uma tem um preço de oferta e um preço de venda, compreendendo: um mecanismo de negociação de par para determinar o lance de oferta no mercado de A dita primeira segurança e a dita segunda segurança. determinar a propagação de pedido de pedido no mercado da dita primeira segurança e da dita segunda segurança. determinar que o limite de propagação mínimo de cada pedido de comércio de pares é atingido por uma gama da dita oferta de licitação e a dita pedir Espalhar por cada segurança. Executar uma transacção entre uma primeira parte da transacção da referida primeira segurança na referida solicitação de comércio de um par e pelo menos uma solicitação de negociação sem par, desde que a mini O limite de propagação do referido pedido de comércio de um par é satisfeito pelo referido intervalo do referido spread de oferta de compra e do referido spread de pedido de pedido e. uma rede de cruzamento de pares para combinar uma segunda porção do referido comércio da referida primeira segurança no referido pedido de comércio de um par e Pelo menos uma primeira porção do comércio da referida segunda segurança na referida solicitação de comércio de um par contra a referida outra solicitação de comércio de pares, desde que uma gama do limite mínimo de propagação da referida solicitação de comércio de um par ea referida outra solicitação de comércio de pares se sobreponha com a referida gama de Em que o dito motor de troca de par transfere a dita transacção para a dita primeira porção do comércio da dita primeira garantia no dito pedido de pedido de um par para Execução no referido mercado externo através da referida ligação.26 O sistema da reivindicação 24 compreendendo ainda uma instituição financeira que tem um inventário de ordens e em que o referido motor de negociação de pares executa a referida transacção N para a referida primeira porção do comércio da referida primeira segurança na referida solicitação de comércio de um par contra o referido inventário de ordens.27 Sistema da reivindicação 24, em que o referido mecanismo de negociação de pares determina se o preço de oferta da primeira garantia na referida solicitação de comércio de um par e O preço de oferta da segunda garantia na referida solicitação de comércio de um par satisfaz um limite de propagação determina uma quantidade da segunda garantia que pode ser vendida com base num tamanho de lance associado com a segunda segurança calcula uma quantidade equivalente da referida primeira garantia que pode ser comprada Baseado na quantidade da referida segunda segurança que pode ser vendida ajusta a referida quantidade equivalente da referida primeira segurança com base em critérios de ajustamento calcula um preço de compra para a referida quantidade equivalente ajustada da referida primeira segurança com base no limite de propagação executa uma ordem inicial para comprar a referida Equivalente da referida primeira garantia ao referido preço de compra e executa uma ordem de cobertura para vender a referida quantidade da segunda garantia.28 Sistema de acordo com a reivindicação 27, em que o mecanismo de negociação de pares executa uma ordem de cobertura para vender a referida quantidade da segunda garantia ao preço de oferta da segunda garantia.29 Sistema da reivindicação 27, em que o mecanismo de negociação de pares determina se o preço de pedido da primeira garantia E o preço de venda do segundo limite de segurança de acordo com um limite de spread determina um montante do primeiro título que pode ser comprado com base num tamanho de oferta associado ao primeiro valor de segurança calcula um montante equivalente do referido segundo valor que pode ser vendido com base no montante de A segunda seguranï¿½ que pode ser comprada ajusta a referida quantidade equivalente da referida segunda seguranï¿½ com base em critï¿½ios de ajustamento calcula um preço de venda para a referida quantidade equivalente ajustada da referida segunda seguranï¿½ com base no limite de espalhamento executa uma ordem de iniciaï¿½o para vender a referida quantidade equivalente ajustada da referida segunda Segurança ao referido preço de venda e executa uma ordem de cobertura para adquirir o referido montante da primeira garantia.30 O sistema de reivindicação 29, em que o mecanismo de negociação de par executa uma ordem de cobertura para adquirir a referida quantidade da primeira garantia ao preço de pedido da primeira garantia.31 Sistema da reivindicação 27, em que os referidos critérios de ajustamento incluem uma quantidade mínima e uma quantidade máxima.32 O sistema de Reivindicação 31, em que o mecanismo de negociação de par troca a referida ordem de iniciação para um tamanho de lote redondo.33 Sistema de acordo com a reivindicação 24, em que o mecanismo de negociação de pares executa pelo menos uma parte da transacção de um dos referidos títulos numa das referidas Pluralidade de parcelas.34 Sistema de acordo com a reivindicação 24, em que a referida solicitação de comércio de um par tem um primeiro limite de propagação e a referida outra solicitação de troca de pares tem um segundo limite de propagação e em que a rede de cruzamento de pares determina que uma gama do referido primeiro limite de propagação e do referido segundo As sobreposições de limite de spread com um spread de mercado definem um nível de spread calcula os preços para a primeira segurança ea segunda segurança que estão dentro da margem de mercado e com base no referido nível de spread e matc A segunda porção do referido comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos uma primeira porção da transacção da referida segunda segurança na referida solicitação de comércio de um par contra outra da referida pluralidade de pedido de comércio de pares com base nos referidos preços calculados. Sistema de acordo com a reivindicação 34, em que a rede de cruzamento de pares calcula uma média entre o referido primeiro limite de propagação e o referido segundo limite de propagação e define o referido nível de propagação como a referida média se a referida média estiver dentro da referida propagação de mercado.36 Sistema da reivindicação 35, Em que a referida rede de cruzamento de pares identifica uma quantidade de spread que está mais próxima da referida média e dentro da referida margem de mercado e define o referido nível de spread como a referida quantidade de spread se a referida média não estiver dentro da referida propagação de mercado. Um primeiro spread limite, uma relação de compra e uma relação de venda, disse que outro pedido de comércio de pares tem um segundo limite de spread, uma relação de compra e uma relação de venda e em que a rede de cruzamento de pares determina que s Ajuda e a referida relação de venda associada à referida solicitação de comércio de um par não igual à referida relação de compra e à referida relação de venda da referida outra solicitação de comércio de pares e que existe uma sobreposição entre a gama do referido primeiro limite de propagação e o referido segundo limite de propagação e uma O spread de mercado determina que existem preços de mercado que estão dentro da sobreposição, determina uma quantidade de desadaptação na referida segunda segurança com base numa diferença entre a referida relação de compra e a referida relação de venda associada à referida solicitação de comércio de um par e a referida relação de compra e a referida relação de venda da referida outra Par que calcula uma quantidade cruzada para a referida primeira segurança e a referida segunda segurança selecciona um preço de cruzamento para a referida primeira segurança e a referida segunda segurança que está dentro da referida sobreposição determina que a referida quantidade de incompatibilidade está disponível no referido preço de cruzamento para a referida segunda Parte do referido comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos a referida primeira parte da transacção Da dita segunda segurança na referida solicitação de comércio de um par contra a dita outra solicitação de comércio de pares com base nos ditos preços seleccionados e executa uma transacção para a dita quantidade de não correspondência da dita segunda segurança ao dito preço de cruzamento para a dita segunda segurança.38 Sistema da reivindicação 37, Par determina que a referida quantidade de desadaptação está disponível num mercado externo ao referido preço de cruzamento para a referida segunda segurança.39 Sistema da reivindicação 37 em que a rede de cruzamento de pares determina que a referida quantidade de desadaptação está disponível ao referido preço de cruzamento para a referida segunda segurança em O referido inventário de ordem de uma instituição financeira.40 O sistema da reivindicação 24, em que a referida solicitação de comércio de um par e a referida outra solicitação de comércio de pares indicam um número de spreads e em que a rede de cruzamento de pares corresponde à referida segunda porção do referido comércio da referida primeira segurança em O referido pedido de troca de um par e pelo menos a referida primeira porção do comércio da referida segunda segurança no referido pedido de um par de comércio T contra o referido outro pedido de troca de pares se o referido número de spreads é maior do que um número mínimo de spreads.41 Sistema de acordo com a reivindicação 24, em que a dita pluralidade de pedidos de comércio de pares inclui pelo menos alguns pedidos de comércio de pares indicando uma preferência pela execução através do dito cruzamento de pares O referido sistema compreendendo ainda um gestor de carteira em comunicações com a referida rede de cruzamento de pares, o referido gestor de carteira recebendo a referida pluralidade de pedidos de comércio de pares e encaminhando pelo menos uma parte da referida pluralidade de pedidos comerciais para a referida rede de cruzamento de pares de acordo com a referida preferência. Sistema de acordo com a reivindicação 24, o dito sistema compreendendo ainda um mecanismo de negociação de pares para executar pelo menos uma parte da dita pluralidade de pedidos de comércio de pares, o dito sistema compreendendo ainda um gestor de portfólio em comunicação com o dito motor de troca de pares, em que a dita pluralidade de pedidos de comércio de pares inclui, Pelo menos alguns pedidos de comércio de pares indicando uma preferência para a execução através do referido mecanismo de negociação de pares, O referido gestor de carteira recebendo a dita pluralidade de pedidos de comércio de pares e encaminhando pelo menos uma parte da dita pluralidade de pedidos de comércio para o dito motor de troca de pares de acordo com a dita preferência.43 O método da reivindicação 24 em que um cliente submete uma consulta relativa ao estado do dito par Comércio e o estado da referida solicitação de troca de pares é continuamente actualizado em tempo real.44 O método da reivindicação 41, em que a referida preferência é apresentada por um cliente electronicamente.45 Método de acordo com a reivindicação 24, em que um cliente recebe um relatório simultâneo quando o referido comércio de pares Pedido é preenchido e o cliente confirma o referido comércio de pares electronicamente.46 Um meio de armazenamento legível por computador armazenando instruções para cumprir um pedido de troca de pares que, quando executado por um computador, faz com que o computador receba uma pluralidade de pedidos de comércio de pares, compreendendo um par Pedido de comércio e outro pedido de comércio de pares, em que cada pedido de comércio de pares compreende um pedido para transaccionar uma primeira garantia, um pedido de transacção E um pedido para trocar a dita primeira segurança e a dita segunda segurança com um limite mínimo de propagação, e em que a dita primeira segurança e a dita segunda segurança cada uma tem um preço de oferta e um preço de pedido. Determinar o lanço de lance de oferta no mercado da dita Primeira segurança e dito segundo security. determine o perguntar perguntar propagação no mercado da dita primeira segurança e dito segundo security. determine que o limite mínimo de propagação de cada pedido de comércio de par é satisfeita por um intervalo de dito lote propagação de oferta e dito pedir pedir spread Executar uma transacção entre uma primeira porção do comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos uma solicitação de comércio sem par, desde que o limite mínimo de propagação da referida solicitação de comércio de um par seja atingido pela gama dos referidos O spread de oferta de oferta e o referido pedido de pedido de spread and. match uma segunda porção do referido comércio da referida primeira segurança na referida solicitação de comércio de um par e pelo menos uma primeira parte da transacção da referida segunda segurança na referida req Uest contra a referida outra solicitação de comércio de par, desde que uma gama do limite mínimo de propagação da referida solicitação de comércio de um par e da referida outra solicitação de comércio de par se sobreponha com a referida gama da referida propagação de lance de oferta e da referida solicitação de pedido spread. CROSS-REFERENCE TO RELATED APPLICATION . Este pedido reivindica o benefício da data de depósito da aplicação provisória dos EUA Ser 60 334 163 intitulada Método e Sistema para Pares Comerciais de Valores Mobiliários, que foi arquivada em 29 de Novembro de 2001, cujo conteúdo é aqui incorporado por referência. Refere-se a um sistema e método para negociar valores mobiliários e, em particular, para um sistema e método de negociação de títulos em pares. Uma estratégia reconhecida para negociação de títulos é conhecida como par-trading. Investidor identifica dois títulos com características semelhantes e os valores mobiliários estão actualmente a negociar numa relação de preços que está fora da sua gama histórica de negociação. Investidor explora a relação de preço entre os valores mobiliários comprando a segurança desvalorizada enquanto vendendo em curto a segurança sobrevalorizada. Como a negociação de pares é uma estratégia neutra de mercado, é uma estratégia particularmente desejável para investir em mercados voláteis. Útil é onde um investidor deseja aproveitar uma oportunidade de arbitragem resultante de uma fusão entre duas empresas. Por exemplo, a Companhia A anunciou um acordo definitivo para adquirir a Companhia T, caso em que os acionistas da Companhia T receberão 0 5 ações da Companhia. Cada ação da Companhia T ações que eles próprios O investidor deseja capturar o spread entre a oferta oferecida 0 5 ações de A eo preço de ações T Para fazer isso, o investidor compra ações em ações T e vende ações de uma ação. Por exemplo , Se o estoque T está sendo negociado em 28 por ação eo estoque A está sendo negociado em 60 por ação, então o investidor pode executar um comércio por 200.000 spreads comprando 200.000 s Lebres de ações T e vender 100.000 ações de uma ação Após a fusão ocorre, o investidor irá cobrir a posição curta em estoque A com as 100.000 ações de uma ação que os investidores recebe em troca das 200.000 ações que o investidor detidas de ações T Assim , Executando o par de negociação, o investidor trava em um lucro de 400.000, supondo que a fusão passa O processo de execução de um comércio de pares, portanto, inclui a execução de negócios individuais direcionados a cada perna do par pedido de comércio Um exemplo de um sistema de execução de negócios para Preenchendo um pedido de troca de par é o sistema Quantex da ITG de 380 Madison Avenue New York, NY 10017. Um desafio na implementação de um comércio de pares é encontrar uma contraparte para uma posição particular que um investidor deseja estabelecer enquanto minimiza o risco de perna Normalmente, Par é realizado fora do mercado como uma transação privada negociada por uma instituição financeira que presta serviços a grandes clientes Por exemplo, se um investidor deseja executar ap O comércio aéreo apostando que uma fusão proposta entre duas empresas irá passar, o investidor iria abordar uma instituição financeira à procura de um investidor que está disposto a apostar contra a fusão A instituição financeira, em seguida, atua como um intermediário entre os dois investidores em que os investidores estabelecer igual E posições opostas no estoque dos sócios de fusão propostos completando desse modo o comércio de pares Assim, ao combinar duas solicitações de comércio de pares de modo que as transações associadas a cada uma das paridades de comércio de pares sejam executadas simultaneamente, nenhum investidor está exposto a risco de perna que de outra forma resultaria Para o período de tempo entre a execução da primeira etapa ea segunda perna do par trade. There são inúmeras desvantagens associadas com a prática de negociação prevalente em primeiro lugar, par-trading é normalmente limitada a clientes de grandes instituições financeiras que têm a capacidade Para identificar contrapartes adequadas para um determinado comércio de pares. N o comércio de par envolve uma grande quantidade de ações ou ações ilíquidas em que a única maneira de executar o comércio e minimizar o risco perna é através de uma transação fora do mercado negociado por uma instituição financeira Também, porque um par de negociação é normalmente negociado pela Partes com uma instituição financeira como um intermediário, o processo é muitas vezes lento e ineficiente Além disso, negociação de par em prática corrente é geralmente mais adequado para grandes clientes que procuram estabelecer grandes posições, proporcionando assim as instituições financeiras com o incentivo econômico para executar a operação. Os clientes devem confiar nos mercados para a execução de negócios de par, o que é inadequado para ações ilíquidas e também resulta em aumento do risco de perna. Em conseqüência, é desejável fornecer um sistema e método para negociar títulos em pares. SUMÁRIO DA INVENÇÃO. A presente invenção é dirigida para superar as desvantagens das práticas comerciais de par de técnicas anteriores. method is provided for fulfilling a pair trade request and includes the steps of receiving a plurality of pair trade requests executing a transaction for a first portion of one of the plurality of pair trade requests and matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests. In an exemplary embodiment, the method includes the step of executing a transaction for a first portion of one of the plurality of pair trade requests in an external market. In another exemplary embodiment, the method includes the step of executing a transaction for a first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request includes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and the method includes the steps of determining whether the bid price of the first security and the bid pr ice of the second security meet a spread limit determining an amount of the second security that can be sold based on a bid size associated with the second security calculating an equivalent amount of the first security that can be bought based on the amount of the second security that can be sold adjusting the equivalent amount of the first security based on adjustment criteria calculating a purchase price for the adjusted equivalent amount of the first security based on the spread limit executing an initiating order to buy the adjusted equivalent amount of the first security at the purchase price and executing a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the method includes the step of executing a covering order to sell the amount of the second security at the bid price of the second security. In an exemplary embodiment, the method includes the steps of determining whether the ask price of the first security and the ask price of the second security and or the bid price of the first security and the bid price of the second security meet a spread limit determining an amount of the first security that can be bought based on an offer size associated with the first security calculating an equivalent amount of the second security that can be sold based on the amount of the second security that can be bought adjusting the equivalent amount of the second security based on adjustment criteria calculating a selling price for the adjusted equivalent amount of the second security based on the spread limit executing an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executing a covering order to purchase the amount of the first security. In another exemplary embodiment, the method includes the step of executing a covering order to purchase the amount of the first security at the ask price of the first security. In yet another exemplary embodiment, the adjustment criter ia include a minimum amount and a maximum amount. In still yet another exemplary embodiment, the method includes the step of rounding the initiating order to a round lot size. In an exemplary embodiment, the method includes the step of executing a first portion of one of the plurality of pair trade requests in a plurality of tranches. In another exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of said plurality of trade requests has a second spread limit and wherein the method includes the steps of determining that a range of the first spread limit and the second spread limit overlaps with a market spread setting a spread level calculating prices for the first security and the second security that are within the market spread and based on the spread level and matching the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In yet another exemplary embodiment, the method includes the steps of calculating a mean between the first spread limit and the second spread limit and setting the spread level as the mean if the mean is within the market spread. In still yet another exemplary embodiment, the method includes the step of identifying a spread amount that is closest to the mean and within the market spread and setting the spread level as the spread amount if the mean is not within the market spread. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and the method includes the steps of determining that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determining that market prices exist that are within the overlap determining a mismatch amount in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculating a cross amount for the first security and the second security selecting a crossing price for the first security and the second security that is within the overlap determining that the mismatch amount is available at the crossing price for the second security matching the second portio n of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices and executing a transaction for the mismatch amount of the second security at the crossing price for the second security. In another exemplary embodiment, the method includes the step of determining that the mismatch amount is available in an external market at the crossing price for the second security. In yet another exemplary embodiment, the method is performed by a financial institution having order inventory and includes the step of determining that the mismatch amount is available in the order inventory at the crossing price for the second security. In still yet another exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and the method includes the step of matching a second portion of the one of the plurality of pair trade requests against anot her of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In an exemplary embodiment, the method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of executing a transaction for a first portion of one of the plurality of pair trade requests, described above. In another exemplary embodiment, the method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests, described above. Under the present invention, a method for fulfilling a pair trade request is provided and includes the steps of receiving a plurality of pair trade requests and matching at least a portion of one of the plurality of pair trade requests against another of the plurality of pair trade requests. Under the pr esent invention, a system for fulfilling a pair trade request is provided, the system receiving a plurality of pair trade requests and includes a pair trading engine for executing a transaction for a first portion of one of the plurality of pair trade requests The system also includes a pair crossing network for matching a second portion of said one of the plurality of pair trade requests against another of the plurality of pair trade requests. In an exemplary embodiment, the system includes a link to external markets and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests in the external markets. In another exemplary embodiment, the system includes a financial institution having an order inventory and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request in cludes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and wherein the pair trading engine determines whether the bid price of the first security and the bid price of the second security meet a spread limit determines an amount of the second security that can be sold based on a bid size associated with the second security calculates an equivalent amount of the first security that can be bought based on the amount of the second security that can be sold adjusts the equivalent amount of the first security based on adjustment criteria calculates a purchase price for the adjusted equivalent amount of the first security based on the spread limit executes an initiating order to buy said adjusted equivalent amount of the first security at the purchase price and executes a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the pair trading engine executes a covering order to sell th e amount of the second security at the bid price of the second security. In an exemplary embodiment, the pair trading engine determines whether the ask price of the first security and the ask price of the second security meet a spread limit determines an amount of the first security that can be bought based on an offer size associated with the first security calculates an equivalent amount of the second security that can be sold based on the amount of the second security that can be bought adjusts said equivalent amount of the second security based on adjustment criteria calculates a selling price for the adjusted equivalent amount of the second security based on the spread limit executes an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executes a covering order to purchase the amount of the first security. In another exemplary embodiment, the pair trading engine executes a covering order to purchase the amount of the first securi ty at the ask price of the first security. In yet another exemplary embodiment, the pair trading engine rounds the initiating order to a round lot size. In still yet another exemplary embodiment, the pair trading engine executes a first portion of one of the plurality of pair trade requests in a plurality of tranches. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of the plurality of trade requests has a second spread limit and wherein the pair crossing network determines that a range of the first spread limit and the second spread limit overlaps with a market spread sets a spread level calculates prices for the first security and the second security that are within the market spread and based on the spread level and matches the second portion of said one of the pluralit y of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In another exemplary embodiment, the pair crossing network calculates a mean between the first spread limit and the second spread limit and sets the spread level as the mean if the mean is within the market spread. In yet another exemplary embodiment, the pair crossing network identifies a spread amount that is closest to the mean and within the market spread and sets the spread level as the spread amount if the mean is not within the market spread. In still yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and wherein the pair crossing net work determines that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determines that market prices exist that are within the overlap determines a mismatch amount in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculates a cross amount for the first security and the second security selects a crossing price for the first security and the second security that is within said overlap determines that the mismatch amount is available at the crossing price for the second security matches the second portion of the one of the plurality of pair trade requests aga inst another of the plurality of pair trade requests based on the calculated prices and executes a transaction for the mismatch amount of the second security at the crossing price for the second security. In an exemplary embodiment, the pair crossing network determines that the mismatch amount is available in an external market at the crossing price for the second security. In another exemplary embodiment, the pair crossing network determines that the mismatch amount is available in the order inventory at the crossing price for the second security. In yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and wherein the pair crossing network matches a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In still yet another exemplary embodim ent, the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via said pair crossing network, and the system further includes a portfolio manager in communications with the pair crossing network, the portfolio manager receiving the plurality of pair trade requests and routing the at least some pair trade requests to the pair crossing network according to the preference. In an exemplary embodiment, the system includes a pair trading engine for executing at least some of the plurality of pair trade requests, further includes a portfolio manager in communications with the pair trading engine and wherein the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via the pair trading engine, the portfolio manager receiving the plurality of pair trade requests and routing the at least some of the plurality of trade requests to the pair trading engine according to the preferenc e. Under the present invention, a system for fulfilling a pair trade request is provided, wherein the system receives a plurality of pair trade requests and includes a pair crossing network for matching at least one of the plurality of pair trade requests against another of the plurality of pair trade requests. Accordingly, a method and a system are provided for trading pair securities. The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims Other features and advantages of the invention will be apparent from the description, the drawings and the claims. DESCRIPTION OF THE DRAWINGS. For a fuller understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings, in which. FIG 1 is a block diagram of a system for trading securities in pairs accordi ng to the present invention. FIG 2 is a flowchart of the steps a pair trading engine included in the system of FIG 1 applies to fill a pair trade request. FIG 3 is a flowchart of the steps a pair crossing network included in the system of FIG 1 applies to fill a pair trade request. FIG 4 is a flowchart of a process by which the pair crossing network of the system of FIG 1 fills imperfectly matched orders and. FIG 5 is a graph for identifying the market prices for two securities that meet the required spread limits. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS. Referring now to FIG 1 there is shown a block diagram of a system 1 for trading securities in pairs according to the present invention System 1 receives pair trade requests from clients operating client access devices 7 and attempts to fill the pair trade requests according to the parameters associated with the particular pair trade request System 1 includes two different subsystems for filling pair trade requests a pair trading e ngine 3 and a pair crossing network 5 As will be described below, pair trading engine 3 receives a pair trade request and attempts to fill in whole or in part the trade request by executing the appropriate trades in an external market 13 that may include, by way of non-limiting example, the New York Stock Exchange, the NASDAQ or any other financial market Pair trading engine 3 may also fill in whole or in part a pair trade request by executing a transaction against order inventory 11 of non-pair trade requests controlled by the financial institution that is operating system 1 In addition, pair trading engine may also fill in whole or in part a pair trade request by forwarding the trade request to pair crossing network 5 for matching with other pair trade requests. Likewise, pair crossing network 5 receives a pair trade request and fulfills in whole or in part the request by matching it against another pair trade request received by pair crossing network 5 by matching the request against inventory 11 controlled by the financial institution and or by forwarding the trade request to pair trading engine 3 for execution in external markets 13.System 1 also includes a portfolio manager 9 that may be, for example, a software program executing on a computer system that receives the pair trade requests from client access device 7 and presents the trade request to either pair trading engine 3 pair crossing network 5 or both, depending on the trade parameters set by the client Also, the client may query portfolio manager 9 regarding the status of any pair trade request the client has presented to system 1.In operation, system 1 may fulfill a pair trade request either using pair trading engine 3 or pair crossing network 5 or a combination of the two For example, a pair trade request received by system 1 may be completely filled by pair trading engine 3 as follows. Assume a case where XYZ is taking over ABC and is offering 0 575 shares of XYZ for each ABC share and investor Arb wa nts to invest in the price difference between ABC stock and XYZ stock To take advantage of the price difference, Arb wants to lock in the difference between the value offered 0 575 XYZ stock and the value of ABC stock by buying ABC stock and selling XYZ stock subject to the condition that ABC 0 575 XYZ 1 19 i e Arb desires to capture a 1 19 difference between XYZ s takeover offer and ABC s share price. In order to fill this pair trade, Arb presents a pair trade request to portfolio manager 9 using client access device 7 The pair trade request typically includes a number of parameters that define the pair trade and that also may be used by portfolio manager 9 in determining how the pair trade request is to be filled Arb typically indicates in the trade request the number of spreads the Arb desires to invest in and also provides a minimum and maximum share amount that he is willing to trade per tranche. For example, Arb may indicate a desire to invest in 100,000 spreads and may only wish t o trade the spread 3,000-8,000 shares at a time Arb generally sets this tranche size range based on the liquidity and volatility of ABC stock and XYZ stock Arb may set a larger minimum tranche size if ABC stock and XYZ stock are fairly liquid stocks because higher liquidity increases the likelihood that a larger tranche size will be executed Arb may set a lower maximum tranche size if XYZ stock and ABC stock are volatile stocks so as to limit the leg risk associated with executing a pair trade. Yet another pair trade parameter Arb provides is the spread limit in the above case 1 19 which is the amount Arb desires to capture in the trade Arb does not have to provide, however, the discrete prices at which trades for ABC and XYZ stock are to be executed as these prices are calculated by pair trading engine 3 and or pair crossing network 5 , as will be described below. Referring now to FIG 2 there is shown a flowchart describing the steps pair trading engine 3 applies to fill a pair trade re quest The flowchart in FIG 2 is based on the above example and the market data listed in Table 1 below. Initially, in Step 201 pair trading engine 3 determines whether the bid bid prices or ask ask prices of ABC and XYZ stock, respectively, meet the spread limit requirement of the particular pair trade request In this case the bid bid spread is 1 4375 122 50 0 575 69 and the ask ask spread is 1 1969 122 625 0 575 69 3125 so that each spread is less than the spread limit of 1 19, as is required for this particular trade Once it is determined that either the bid bid spread or the ask ask spread meets the spread limit, then in Step 202 it is determined as is indicated in Table 1 how much XYZ stock can be sold at the bid and how much ABC stock can be bought at the ask In an exemplary embodiment, the client may specify whether the bid bid spread, the ask ask spread or either the bid bid or the ask ask spread must exceed the indicated spread limit for a transaction to proceed If neither the b id bid spread nor the ask ask spread meets the spread limit, the process waits a period of time for example 0 10 seconds and returns to Step 201 to again test whether the bid bid spread or the ask ask spread meets the spread limit. Next, in step 203 an equivalent amount of stock that can be sent into the market i e bought sold in the market is calculated for a spread based on the bid bid price spread and or the ask ask price spread that meets the spread limit In this example, if a maximum of 10,000 shares of XYZ stock can be sold into the market i e the XYZ bid size then, based on the ABC XYZ ratio of 1 0 575 in this case , a total of 17,391 10,000 0 575 shares of ABC stock are to be bought in order to execute a balanced pair trade Likewise, if a maximum of 1,500 shares of ABC stock can be bought in the market i e the ABC ask size , then, based on the ABC XYZ ratio of 1 0 575 in this case , a total of 863 1500 0 575 shares of XYZ stock are to be sold in order to execute a balanced pair trade. Next, in Step 204 the pair trade share amounts calculated in Step 203 are adjusted to conform to the wave maximum and minimum parameters i e the maximum minimum tranche size included in the pair trade request as well as market round lot limits In the above example, the amount of ABC shares to be bought that was calculated based on the XYZ bid size i e 17,391 is first rounded to an even lot size i e 17,400 and then reduced to the maximum tranche size of 8000 Also, the amount of XYZ shares to be offered that was calculated based on the ABC ask size i e 863 is first rounded to an even lot size i e 900 and then increased to 1,700 shares to meet the minimum tranche size of 3000 3000 0 575 1777 In an exemplary embodiment the minimum and maximum tranche size is scaled by the particular ratio for example, in the above case, the tranche sizes for XYZ stock is scaled by 0 575 In another embodiment, the maximum minimum tranche size is used for each security in the pair trade request without scaling In yet another exemplary embodiment, the pair trade request includes a separate maximum minimum tranche for each security. Once the share amounts for the pair trade are calculated, in Step 205 the share prices that are needed to meet the spread limit of the pair trade request are calculated For example, for a pair trade based on the bid bid price spread, in order to meet the spread limit of 1 19 credit, the price at which ABC stock is to be bid should be no greater than 69 2475 122 50 0 575 1 19 a share Likewise, for a pair trade based on the ask ask price spread, in order to meet the spread limit, the price at which XYZ stock is to be offered should be greater than or equal to 122 6130 69 3125 1 19 0 575 a share. Next, once the pair trade share amounts and share prices have been calculated, in Step 206 pair trading engine 3 sends initiating orders to external markets 13 in order to fill the pair trade request The initiating orders may include an initiating order for executing a pair trade based on the bid bid spread in this case a bid for 8,000 shares of ABC stock at 69 2475 and or an initiating order for executing a pair trade based on the ask ask spread in this case an offer of 1,700 shares of XYZ stock at 122 6130.Finally, as the initiating orders sent to external markets 13 in Step 207 get filled, pair trading engine 3 automatically sends into the market the covering side of the pair trade So, for example, as the initiating order of buying 8,000 shares of ABC stock at 69 2475 gets filled, pair trading engine 3 sends an order to external markets 13 to sell 4,600 8,000 0 575 shares of XYZ stock at 122 50.In an exemplary embodiment, the client s pair trade request includes threshold amounts that indicate the amount of variance in stock price and or share amount the client is willing to absorb For example, if in the process of covering the initiating order the price of XYZ stock dips to 122 49 in which case the spread limit of the pair trade would drop to 1 18 , then pair trading engine 3 would still sell XYZ stock at the price of 122 49 if the 0 01 difference was within the threshold amount included in the pair trade request Similarly, the pair trade request may include threshold amounts for any other pair trade parameter, including by way of non-limiting example, the number of spreads to be purchased and the tranche sizes If, however, a particular threshold amount indicated by the client is exceeded for any given pair trade parameter, then pair trading engine 3 would attempt to cancel the initiating order and or the covering order that may be possible if the orders have not yet reached the market or have not yet been filled In such a case, pair trading engine 3 would then repeat the above analysis for determining suitable initiating and cover orders. To fill a pair trade request, pair trading engine 3 executes trades utilizing the method described above Typically, pair trading engine 3 tranches a pair trade request and trades piece-meal in external markets 13 In certain cases, however, it may be difficult to fill a trade request by executing several transactions in external markets 13 either because the pair trade request is for a very large number of spreads or includes stocks that are illiquid in which cases pair trading engine 3 may be ineffective in filling the pair trade request Also, in certain situations, a client wishing to remain anonymous may indicate in the pair trade request a preference that no orders be sent to external markets 13 In these circumstances, portfolio manager 9 may route the particular pair trade request to pair crossing network 5.Referring now to FIG 3 there is shown a flowchart illustrating the steps pair crossing network 5 applies to fill a pair trade request The flowchart in FIG 3 is based on the above example and the market data listed in Table 2 below. Spread Limit as defined by 0 575 XYZ - ABC. Continuing the previous example, assume the pair trade request issued by Arb for 100,000 spreads was half-filled by pair trading engine 3 Also, assume that system 1 receives a pair trade request from Antiarb that indicates a desire to sell 30,000 shares of ABC and buy 17,200 shares a ratio of 1 0 575 and also indicates a spread limit of 1 30 i e ABC 0 575XYZ 1 30 In this case Arb and Antiarb s orders are complimentary in the primary order elements securities, ratios and buy versus sell Also, Antiarb is willing to pay 0 11 per spread more than Arb is demanding from the marketplace Based on these parameters, there is an opportunity for Arb s and Antiarb s trade requests to be filled via pair crossing network 5.If Antiarb s pair trade request was marked for trading by pair trading engine 3 then portfolio manager 9 sends Antiarb s order to pair trading engine 3 for execution Pair trading engine 3 then sends the parameters of Antiarb s trade reques t, as well as all orders waiting for execution in pair trading engine 3 to pair crossing network 5 Pair crossing network 5 will recognize as described above that there is a crossing opportunity between Arb s order and Antiarb s order In this case, pair crossing network 5 then directs pair trading engine 3 to suspend the execution of Antiarb s order in the amount that can be crossed by pair crossing network 5 30,000 spreads in this case In addition, pair trading engine 3 routes a cross amount of 30,000 spreads from Arb s order to pair crossing network 5 for crossing against Antiarb s order At this point, the pair crossing network 5 crosses the Antiarb order against a portion of Arb s order, as follows. Assume the prevailing market conditions at the time of the cross are as shown in Table 3 Furthermore, Table 3 indicates the XYZ Ratio-Adjusted Value for both the bid and ask prices based on the conversion ratio of 1 0 575 Based on the XYZ Ratio-Adjusted Values, a Bid Ask Spread Range i e t he spread provided for a cross between the bid price of ABC stock and the XYZ Ratio-Adjusted ask price of 1 3863 is calculated and an Ask Bid Spread Range i e the spread provided for a cross between the ask price of ABC stock and the XYZ Ratio-Adjusted bid price of 1 05 is calculated. To perform the cross, in Step 301 pair crossing network 5 first determines whether the range of spread limits associated with Arb s and Antiarb s trade requests i e 1 30- 1 19 coincides with the range of the prevailing market spread 1 3863- 1 05 In this example, the range of spread limits does coincide with the prevailing market spread because at least a portion of the spread limit range overlaps with a portion of the market spread Thus, a cross can occur. Next, in Step 302 pair crossing network 5 calculates the mean of Arb s and Antiarb s spread order limit which is 1 30 1 19 2 1 245 and determines whether the mean is within the range of the market spread i e 1 3863- 1 05 If it is, then in Step 303 pair cr ossing network 5 calculates the prices at which to cross The prices must be within the current markets for ABC stock and XYZ stock, and satisfy market uptick requirements for short sales , and provide a spread that is equal to the spread level calculated above For example, with the inside market for ABC stock at 70 00-70 25 and the inside market for XYZ stock at 124 00-124 15, a cross price of 70 11 for ABC stock and 124 096 for XYZ stock provides the spread of 1 2452 thereby meeting the requirement of both Arb s and Antiarb s trade request Finally, in Step 304 pair crossing network 5 crosses 30,000 shares of ABC stock at 70 11 with Arb buying and Antiarb selling and 17,200 shares of XYZ at 124 096 with Arb selling and Antiarb buying. If it is determined in Step 302 that the mean of Arb s and Antiarb s spread order limits does not fall within the range of the market spread, then in Step 305 the spread closest to the mean of the two spread limits that is also within the market spread is calculated For example, if the market spread is 1 3863- 1 28, then the mean of the two spread limits 1 245 is not within the market spread In such a case, 1 28 is selected as the spread level that is closest to the mean and within the market spread In an exemplary embodiment, the spread level at which Arb and Antiarb cross can be determined in any other suitable manner as long as the spread level is within the market spread and within the range of spread limits indicated in the pair trade requests. Once the spread level is determined, the method proceeds to Step 303 in which pair crossing network 5 calculates prices to cross at that are within the current markets for ABC stock and XYZ stock and that meet the calculated spread level In the case where the calculated spread level is 1 28, the cross will occur at a price of 70 08 for ABC stock and 124 1043 for XYZ stock Finally, the method proceeds to Step 304 in which pair crossing network 5 performs the cross between Arb and Antiarb. Once a pair trade request is filled or partially filled , the transaction details are reported to portfolio manager 9 and made available to the client operating client access device 7.In the previous example, pair crossing network 5 crosses orders in which both Arb and Antiarb desire to trade the same pair of securities in the same ratio In an exemplary embodiment, pair crossing network 5 executes a cross between two pair trade requests that are not perfectly matched. For example, assume that pair crossing network 5 receives the pair trade requests as shown in Table 4 Note that these two pair trade requests are imperfectly matched because each trade request uses a different ratio between ABC and XYZ stock. Arb s Spread Limit is defined by 0 575 XYZ - ABC. Antiarb s Spread Limit is defined by 0 6 XYZ - ABC. Also, assume the market in ABC and XYZ stocks at the time the pair trade requests are received by pair crossing network 5 is as described in Table 5 below. Arb s XYZ Ratio-Adjusted Value. Arb s Dollar Range. AntiArb s XYZ Ratio-Adjusted Value. AntiArb s Dollar Range. Referring now to FIG 4 there is shown a flowchart illustrating a process by which pair crossing network 5 fills these imperfectly matched order First, in Step 401 pair crossing network 5 determines whether Arb s buy security equals Antiarb s sell security and whether Arb s sell security equals Antiarb s buy security If both conditions are not met, then a cross between the two orders cannot occur If the two conditions are met, then in Step 402 it is determined whether Arb s buy ratio equals Antiarb s sell ratio and whether Arb s sell ratio equals Antiarb s buy ratio If these ratios are the same, then pair crossing network 5 procee ds to cross the two orders as described in the example above Note that for a cross to occur at this stage does not require the ratios themselves to match but rather that the ratios of the ratios match for e g a ratio of 2 3 matches a ratio of 0 667 1.If, however, the two ratios are not equal as in this case where Arb s sell ratio does not equal Antiarb s buy ratio , then in Step 403 pair crossing network determines whether there is an overlap between Arb s and Antiarb s spread limit that also falls within the bid ask market for ABC and XYZ stock To make such a determination, pair crossing network 5 calculates whether there are market prices for both ABC and XYZ stock that satisfy the following inequalities L 1 Ratio A ABC Ratio B XYZ and 1 L 2 Ratio C ABC Ratio D XYZ 2 Where L1 is Arb s spread limit of 1 19 credit, L2 is Antiarb s spread limit of 4 40 debit, RatioA is Arb s buy ratio of 1 1, RatioB is Arb s sell ratio of 1 0 575, RatioC is Antiarb s sell ratio of 1 1 and RatioD is Anti arb s buy ratio of 1 0 6.Referring now to FIG 5 there is shown a graph 51 that depicts market prices for ABC and XYZ stock that meet the spread limits of Arb and Antiarb In graph 51 the x-axis represents the prices for XYZ stock while the y-axis represents the prices for ABC stock Graph 51 includes a shaded area 53 that is the universe of market prices for ABC and XYZ stock that could satisfy the spread trade involving those stocks Also included in graph 53 is a spreadlimit line L1 inequality 1 , above that represents the spread limit associated with Arb and a spread limit line L2 inequality 2 , above that represents the spread limit associated with Antiarb Thus, the solution set of market prices that satisfies inequalities 1 and 2 is the portion of dark shared area 53 that falls between spread limit line L1 and spread limit line L2 In this example, a cross at a share price for ABC of 70 14 and a share price of 124 15 for XYZ stock meets the investor s spread limits and falls within th e market prices for ABC and XYZ stock. If it is determined that no share prices for both ABC and XYZ stock satisfy Arb s and Antiarb s spread limits, then no cross can occur If such share prices do exist, then in Step 404 it is determined which of the investors desires to transact in fewer shares of ABC stock and a mismatch in share amounts caused by the differing ratios is determined In our example, Antiarb desires to sell fewer ABC shares than Arb desires to buy 30,000 vs 50,000 Then, in Step 405 pair crossing network 5 determines the number of XYZ shares that can be crossed between Arb and Antiarb based on the maximum amount of ABC shares that can be crossed 30,000 in this example Based on the Antiarb ABC order quantity of 30,000 shares, the maximum number of XYZ shares that Arb will cross with Antiarb is.30 000 Arb XYZ Ratio Arb ABC Ratio 30 000 0 575 1 17 300 17 250 rounded to an even lotsize. While the maximum quantity of XYZ shares that Arb will cross is 17,300, Antiarb s trade re quest indicates a desire to cross 18,000 shares To overcome this imbalance, in Step 406 pair crossing network 5 is in communications with external markets 13 for determining whether the excess 700 XYZ shares needed to satisfy Antiarb s trade request can be transacted for in external markets 13 In an exemplary embodiment, pair crossing network 5 makes this determination by issuing a query to pair trading engine 3 as to whether 700 shares of XYZ stock can be bought in external markets 13 Because, as indicated in Table 5, 3,000 shares of XYZ stock are offered at 124 15, pair trading engine 3 responds to pair crossing network 5 that the 700 shares needed to balance the cross between Arb and Antiarb are available from external markets 13 at 124 15.Next, in Step 407 pair crossing network calculates the cross prices that are necessary such that Arb and Antiarb achieve their respective spread limits while also incorporating the excess 700 shares of XYZ stock that must be purchased from externa l markets 13 at 124 15 to satisfy Antiarb s trade request An example of such cross prices that meet these criteria is a price of 70 14 for ABC stock and a price of 124 15 for XYZ stock. Once the cross prices are calculated, in Step 408 pair crossing network 5 crosses 30,000 shares of ABC stock and 17,300 shares of XYZ stock between Arb and Antiarb and also buys 700 shares of XYZ stock at 124 15 in external markets 13 on behalf of Antiarb Thus, both Arb and Antiarb s pair trade requests are satisfied. Alternatively, the entire 18,000 shares of XYZ stock may be crossed thereby fully satisfying Antiarb s trade request In such a case, the ratio mismatch is addressed by Arb purchasing an additional 1200 700 0 575 rounded to a lotsize shares of ABC stock from external market 13 or from firm inventory 11.Once the trade is completed, the details of the transaction are provided to portfolio manager 9 to report the transaction details to the investors. In an exemplary embodiment, a pair order or po rtion thereof may be filled against an internal inventory 11 of trade requests maintained by the financial institution operating system 1 For example, in the previous example in which an excess of 700 shares of XYZ stock needs to be purchased in order for a match i e cross between Arb and Antiarb s trade requests to occur, instead of determining whether the 700 shares are available in external markets 3 pair crossing network 5 examines firm inventory 11 to determine whether the shares are available at the required price Likewise, in cases where pair trading engine 3 desires to execute a pair trade based on orders to be sent to external markets 13 pair trading engine 3 may first determine whether the order can be filled, in whole or in part, using trade requests pending in firm inventory 11 Generally, the advantages of filling an order using pending trade requests in firm inventory 11 is that execution is faster, transaction costs are lower and leg risk is minimized. In another exemplary embodiment, a client s pair trade request may also include a minimum number of spreads that can be traded in pair crossing network 5 Also, pair crossing network 5 may be designed to require a minimum share amount for a cross to occur A minimum number of spreads that can be traded may be provided in order to reduce the distractions and booking costs associated with numerous smaller trades that may exceed the benefits of a de minimis fill. In another exemplary embodiment, portfolio manager 9 publishes the inside cross market for any pair that a client has selected for crossing in pair crossing network 5 In still another exemplary embodiment, the client has the option for each pair trade selected for crossing in pair crossing network 5 to designate that the order should be reflected in the published inside cross market This inside cross market consists of the tightest spread bid and offer and corresponding bid size and offer size from all client pair orders pending in pair crossing networ k 5 In this way, a client can assess the likelihood and timing of a pair trade request being filled by pair crossing network 5 Also, by publishing the client s spread interest, others seeking liquidity can trade at the client s level. In an exemplary embodiment, the client can designate each pair order designated for pair trading engine 3 and or pair crossing network 5 for Broker Negotiation If Broker Negotiation is designated, the client s broker-dealer sales representative is notified of the client s spread order thereby prompting the broker-dealer to solicit a complementary, agency order from another client The client may also designate each pair order for Broker Facilitation in which case the client allows the broker-dealer to act principally to fill the client s order. In summary, the advantages to a client of using pair trading engine 3 is that pair trading engine 3 allows the client to trade a spread order while limiting leg risk or the risk of missing a targeted spread level This is accomplished by breaking the total order into tranches of sizes proportionate to the market, subject to user minimums and maximums, that can be traded in external markets 13 or against firm inventory 11 Orders executed via pair trading engine 3 however, are typically of a lower traded volume because trading is constrained to the liquidity available in the market In contrast, trades executed via pair crossing network 5 are not constrained by market liquidity and do not have to be tranched to minimize leg risk In particular, the benefits of filling a pair trade request via pair crossing network 5 are as follows. Elimination of Leg Risk Pair crossing network 5 potentially provides a deeper well of liquidity because the trades are brokered, as a spread, directly between spread investors via a central clearing facility Moreover, the introduction and use of a pair trading facility eliminates the leg risk described above without a sacrifice of liquidity. Large Transactions Only Certain larg e investors may prefer to use pair crossing network 5 rather than pair trading engine 3 to avoid having a trade request broken up into numerous small executions For example, sudden, brief moves in one of the two stocks included in the pair trade request may cause pair trading engine 3 to issue numerous small executions to fill the request While a small investor may welcome capturing these small opportunities, a large investor may find such small executions to be more of a nuisance than a service. Price Setting versus Price Taking Large investors seeking liquidity may prefer to set their price via the pair crossing network 5 Also, other spread investors looking for liquidity can use pair crossing network 5 to monitor and trade with the large investor at the large investor s level While client orders directed to pair trading engine 3 can designate a spread limit, such orders are essentially price-takers as the market reaches the desired level, the orders are executed Moreover, the pair tr ading engine tranching mechanism creates relatively small orders, allowing institutional flows to move the individual stocks As a result, the small, tranched orders generated by pair trading engine 3 can become overpowered by single-name institutional flows In addition, orders designated solely for pair trading engine 3 and not for pair crossing network 5 are not published to a central quote facility such as by portfolio manager 9 thereby preventing other spread traders from knowing the size and limit of a pair trading engine order. Illiquid Stocks vs Liquid Stocks Spreads that include one or two illiquid stocks are difficult to fill using pair trading engine 3 alone Because illiquid stocks often demonstrate small bid and ask sizes and wide bid-ask spreads, pair trading engine 3 will typically only issue market orders having small quantities subject to user minimums and maximums that presents the client with greater leg risk from mid-trade changes in the bid-ask prices In contrast, orde rs routed to price crossing network 5 are not confined by liquidity in the market place thereby allowing large crosses between spread traders in illiquid spreads. Accordingly, a system and method for trading pair securities is provided in which the client receives the benefits of having a pair order filled by either pair trading engine 3 pair crossing network 5 or a combination of both. A number of embodiments of the present invention have been described Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention Based on the above description, it will be obvious to one of ordinary skill to implement the system and methods of the present invention in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device Each computer program may be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired and in any case, the language may be a compiled or interpreted language Suitable processors include, by way of example, both general and special purpose microprocessors Furthermore, alternate embodiments of the invention that implement the system in hardware, firmware or a combination of both hardware and software, as well as distributing modules and or data in a different fashion will be apparent to those skilled in the art and are also within the scope of the invention In addition, it will be obvious to one of ordinary skill to use a conventional database management system such as, by way of non-limiting example, Sybase, Oracle and DB2, as a platform for implementing the present invention Also, network access devices can comprise a personal computer executing an operating system such as Microsoft Windows , U nix , or Apple Mac OS , as well as software applications, such as a JAVA program or a web browser Access devices can also be a terminal device, a palm-type computer, mobile WEB access device or other device that can adhere to a point-to-point or network communication protocol such as the Internet protocol Computers and network access devices can include a processor, RAM and or ROM memory, a display capability, an input device and hard disk or other relatively permanent storage Accordingly, other embodiments are within the scope of the following claims. It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above process, in a described product, and in the construction set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description shown in the accompanying drawing shall be i nterpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween. A method is provided for fulfilling a pair trade request and includes the steps of receiving a plurality of pair trade requests executing a transaction for a first portion of one of the plurality of pair trade requests and matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests. 20.The invention claimed is.1 A computer-implemented method for fulfilling a pair trade request, said pair trade request performed by a financial institution having an order inventory, the method comprising the steps of. receiving a plurality of pair trade requests, comprising at least one pair trade request, wherein said pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price. determining the bid bid spread in the market of said first security and said second security. determining the ask ask spread in the market of said first security and said second security. determining that the minimum spread limit of said pair trade request is met by a range of said bid bid spread and said ask ask spread. executing a transaction between a first portion of the trade of said first security in said one pair trade request and at least one non-pair trade request in an external market, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread and. executing a transaction between one of a second portion of said trade of said first security in said one pair trade request or a first portion of the trade of said second security in said one pair trade request, and at least one non-pair trade request in said order inventory, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread. wherein at least one of said steps is implemented with a computer.2 The method of claim 1 further comprising. executing a transaction between a portion of the trade of said second security in said one pair trade request and at least another non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread. and wherein the steps of executing said first portion of the trade of said first security in said one pair trade request and executing said portion of the trade of said second security in said one pair trade request include the steps of. determining whether the bid price of the first security and the bid price of the second security meet a spread limit. determining an amount of the second security that can be sold based on a bid size associated with the second security. calculating an equivalent amount of said first security that can be bought based on the amount of said second security that can be sold. adjusting said equivalent amount of said first security based on adjustment criteria. calculating a purchase price for said adjusted equivalent amount of said first security based on the spread limit. executing an initiating order to buy said adjusted equivalent amount of said first security at said purchase price a nd. executing a covering order to sell said amount of the second security.3 The method of claim 2 wherein the step of executing a covering order to sell includes the step of. executing a covering order to sell said amount of the second security at the bid price of the second security.4 The method of claim 2 further comprising the steps of. determining whether the ask price of the first security and the ask price of the second security meet a spread limit. determining an amount of the first security that can be bought based on an offer size associated with the first security. calculating an equivalent amount of said second security that can be sold based on the amount of the second security that can be bought. adjusting said equivalent amount of said second security based on adjustment criteria. calculating a selling price for said adjusted equivalent amount of said second security based on the spread limit. executing an initiating order to sell said adjusted equivalent amount of said second se curity at said selling price and. executing a covering order to purchase said amount of the first security.5 The method of claim 4 wherein the step of executing a covering order to purchase includes the step of. executing a covering order to purchase said amount of the first security at the ask price of the first security.6 The method of claim 4 wherein said adjustment criteria include a minimum amount and a maximum amount.7 The method of claim 4 wherein the step of executing an initiating order includes the step of. rounding said initiating order to a round lot size.8 The method of claim 1 further comprising. executing a transaction between a portion of the trade of said second security in said one pair trade request and at least another non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread. and wherein the steps of executing said first portion of the trade of said first security in said one pair trade request and executing said portion of the trade of said second security in said one pair trade request includes the steps of. determining whether the ask price of the first security and the ask price of the second security meet a spread limit. determining an amount of the second security that can be bought based on an ask size associated with the second security. calculating an equivalent amount of said first security that can be sold based on the amount of the second security that can be bought. adjusting said equivalent amount of said first security based on adjustment criteria. calculating a selling price for said adjusted equivalent amount of said first security based on the spread limit. executing an initiating order to sell said adjusted equivalent amount of said first security at said selling price and. executing a covering order to purchase said amount of said second security.9 The method of claim 1 wherein at least one of the executing steps include the step of. ex ecuting at least a portion of the trade of said first security or said second security in said one pair trade request in a plurality of tranches.10 The method of claim 1 wherein said plurality of pair trade requests comprises another pair trade request, wherein said another pair trade request comprises a request to trade said first security, a request to trade said second security and wherein said one pair trade request has a first spread limit and said another pair trade request has a second spread limit and wherein said method further comprises the steps of. determining that the minimum spread limit of said another pair trade request is met by said range of said bid bid spread and said ask ask spread and. matching another portion of said trade of said first security in said one pair trade request and at least another portion of said trade of said second security in said one pair trade request against said another pair trade request, provided that a range of the minimum spread limit of said one pair trade request and said another pair trade request overlaps with said range of said bid bid spread and said ask ask spread.11 The method of claim 10 wherein said matching step further includes the steps of. determining that a range of said first spread limit and said second spread limit overlaps with a market spread. setting a spread level. calculating prices for the first security and the second security that are within the market spread and based on said spread level and. matching said another portion of said trade of said first security in said one pair trade request and at least said another portion of the trade of said second security in said one pair trade request against said another pair trade request based on said calculated prices.12 The method of claim 11 wherein the step of setting a spread level includes the steps of. calculating a mean between said first spread limit and said second spread limit and. setting said spread level as said mean if said mean is within sai d market spread.13 The method of claim 12 further including the step of. identifying a spread amount that is closest to said mean and within said market spread and. setting said spread level as said spread amount if said mean is not within said market spread.14 A computer-implemented method for fulfilling a pair trade request, comprising the steps of. receiving a plurality of pair trade requests, comprising at least one pair trade request, wherein said pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price. determining the bid bid spread in the market of said first security and said second security. determining the ask ask spread in the market of said first security and said second security. determining that the minimum spread limit of said pair trade re quest is met by a range of said bid bid spread and said ask ask spread. executing a transaction between a first portion of the trade of said first security in said one pair trade request and at least a first non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread. executing a transaction between a first portion of the trade of said second security in said one pair trade request and at least a second non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread and. repeating the executing steps until the pair trade request is fulfilled. wherein at least one of said steps is implemented with a computer.15 The method of claim 14 wherein at least one of the repeated steps includes the step of. executing a transaction for a portion of the trade of said first security in said one pair trade re quest in an external market.16 The method of claim 14 wherein at least one of the repeated executing steps is performed by a financial institution having an order inventory and at least said one of said repeated steps includes the step of. executing a transaction for a portion of the trade of said first security in said one pair trade request against said order inventory.17 The method of claim 14 wherein said plurality of pair trade requests comprises another pair trade request, wherein said another pair trade request comprises a request to trade said first security, a request to trade said second security and a request said first security and said second security with a second minimum spread limit, the method further comprising the steps of. determining that the minimum spread limit of said another pair trade request is met by said range of said bid bid spread and said ask ask spread and. matching a second portion of said trade of said first security in said one pair trade request and at least a first portion of the trade of said second security in said one pair trade request against said another pair trade request, provided that a range of the minimum spread limit of said one pair trade request and said another pair trade request overlaps with said range of said bid bid spread and said ask ask spread.18 A computer readable storage medium storing instructions for fulfilling a pair trade request that, when executed by a computer, cause the computer to. receive a plurality of pair trade requests, comprising at least one pair trade request, wherein said pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price. determine the bid bid spread in the market of said first security and said second security. determine the ask ask spread in the ma rket of said first security and said second security. determine that the minimum spread limit of said pair trade request is met by a range of said bid bid spread and said ask ask spread. execute a transaction between a first portion of the trade of said first security in said one pair trade request and at least one non-pair trade request in an external market, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread and. execute a transaction between one of a second portion of said trade of said first security in said one pair trade request or a first portion of the trade of said second security in said one pair trade request, and at least one non-pair trade request in said order inventory, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread.19 A computer readable storage medium storing instructions for fulfilling a pair tra de request that, when executed by a computer, cause the computer to. receive a plurality of pair trade requests, comprising at least one pair trade request, wherein said pair trade request comprises a request to trade a first security, a request to trade a second security, and a request to trade said first security and said second security with a minimum spread limit, and wherein said first security and said second security each have a bid price and an ask price. determine the bid bid spread in the market of said first security and said second security. determine the ask ask spread in the market of said first security and said second security. determine that the minimum spread limit of said pair trade request is met by a range of said bid bid spread and said ask ask spread. execute a transaction between a first portion of the trade of said first security in said one pair trade request and at least a first non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread. execute a transaction between a first portion of the trade of said second security in said one pair trade request and at least a second non-pair trade request, provided that the minimum spread limit of said one pair trade request is met by said range of said bid bid spread and said ask ask spread and. repeat the executing steps until the pair trade request is fulfilled.20 The method of claim 19 wherein at least one non-pair trade request is selected from the group consisting of an external market order and an order from an inventory from a financial institution. CROSS-REFERENCE TO RELATED APPLICATIONS. This application is a divisional application of U S patent application Ser No 10 206,549, entitled Pair trading system and method , which was filed on Jul 25, 2002 now U S Pat No 7,412,415, which claims priority to U S provisional patent application Ser No 60 334,163 entitled Method and System for Trading Pairs of S ecurities that was filed on Nov 29, 2001 The contents of both applications are herein incorporated by reference. The following invention relates to a system and method for trading securities and, in particular, for a system and method of trading securities in pairs. A recognized strategy for trading securities is known as pair-trading Pair-trading is a non-directional investment strategy in which the investor identifies two securities having similar characteristics and the securities are currently trading at a price relationship that is out of their historical trading range The investor exploits the price relationship between the securities by buying the undervalued security while short-selling the overvalued security Because pair-trading is a market-neutral strategy, it is a particularly desirable strategy for investing in volatile markets. One context in which pair trading is useful is where an investor desires to take advantage of an arbitrage opportunity resulting from a merger betwee n two companies For example, Company A has announced a definitive agreement to acquire Company T in which case Company T shareholders will receive 0 5 shares of Company A stock for each share of Company T stock they own The investor desires to capture the spread between the offered consideration 0 5 shares of A and the price of T stock To do this, the investor buys shares in T stock and sells shares of A stock. For instance, if stock T is trading at 28 per share and stock A is trading at 60 per share, then the investor may execute a trade for 200,000 spreads by buying 200,000 shares of T stock and selling 100,000 shares of A stock After the merger takes place, the investor will cover the short position in stock A with the 100,000 shares of A stock the investors receives in exchange of the 200,000 shares the investor held of stock T Thus, by executing the pair trade, the investor locks in a 400,000 profit assuming that the merger goes through The process of executing a pair trade thus in cludes executing individual trades directed to each leg of the pair trade request An example of a system for executing trades for filling a pair trade request is the Quantex system from ITG of 380 Madison Avenue, New York, N Y 10017.A challenge in implementing a pair trade is to find a counterparty for a particular position an investor desires to establish while minimizing leg risk Typically, a large pair trade is performed off the market as a private transaction negotiated by a financial institution that services large clients For example, if an investor desires to execute a pair trade betting that a proposed merger between two companies will go through, the investor would approach a financial institution seeking an investor that is willing to bet against the merger The financial institution then acts as an intermediary between the two investors in which the investors establish equal and opposite positions in the stock of the proposed merger partners thereby completing the pair trade Thus by matching two pair trade requests so that the transactions associated with each of the pair trade legs are executed simultaneously, neither investor is exposed to leg risk that would otherwise result for the period of time between execution of the first leg and the second leg of the pair trade. There are numerous drawbacks associated with the prevalent pair-trading practice First, pair-trading is typically limited to clients of large financial institutions that have the ability to identify suitable counterparties for a particular pair trade This is especially the case when the pair trade involves a large amount of stock or illiquid stocks in which the only way to execute the trade and minimize leg risk is via an off the market transaction negotiated by a financial institution Also, because a pair-trade is typically negotiated by the parties with a financial institution as an intermediary, the process is often slow and inefficient Furthermore, pair-trading under current practice i s generally best suited for large clients seeking to establish large positions thereby providing the financial institutions with the economic incentive to execute the transaction Smaller clients, however, must rely on the markets for executing pair trades, which is unsuitable for illiquid stocks and also results in increased leg risk. Accordingly, it is desirable to provide a system and method for trading securities in pairs. SUMMARY OF THE INVENTION. The present invention is directed to overcoming the drawbacks of the prior art pair trading practices Under the present invention a method is provided for fulfilling a pair trade request and includes the steps of receiving a plurality of pair trade requests executing a transaction for a first portion of one of the plurality of pair trade requests and matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests. In an exemplary embodiment, the method includes the step of e xecuting a transaction for a first portion of one of the plurality of pair trade requests in an external market. In another exemplary embodiment, the method includes the step of executing a transaction for a first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request includes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and the method includes the steps of determining whether the bid price of the first security and the bid price of the second security meet a spread limit determining an amount of the second security that can be sold based on a bid size associated with the second security calculating an equivalent amount of the first security that can be bought based on the amount of the second security that can be sold adjusting the equivalent amount of the first security based on adjustment criteria calculating a purchase price for t he adjusted equivalent amount of the first security based on the spread limit executing an initiating order to buy the adjusted equivalent amount of the first security at the purchase price and executing a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the method includes the step of executing a covering order to sell the amount of the second security at the bid price of the second security. In an exemplary embodiment, the method includes the steps of determining whether the ask price of the first security and the ask price of the second security and or the bid price of the first security and the bid price of the second security meet a spread limit determining an amount of the first security that can be bought based on an offer size associated with the first security calculating an equivalent amount of the second security that can be sold based on the amount of the second security that can be bought adjusting the equivalent amount of the second security based on adjustment criteria calculating a selling price for the adjusted equivalent amount of the second security based on the spread limit executing an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executing a covering order to purchase the amount of the first security. In another exemplary embodiment, the method includes the step of executing a covering order to purchase the amount of the first security at the ask price of the first security. In yet another exemplary embodiment, the adjustment criteria include a minimum amount and a maximum amount. In still yet another exemplary embodiment, the method includes the step of rounding the initiating order to a round lot size. In an exemplary embodiment, the method includes the step of executing a first portion of one of the plurality of pair trade requests in a plurality of tranches. In another exemplary embodiment, the one of the plurality of pair trade requests a nd the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of said plurality of trade requests has a second spread limit and wherein the method includes the steps of determining that a range of the first spread limit and the second spread limit overlaps with a market spread setting a spread level calculating prices for the first security and the second security that are within the market spread and based on the spread level and matching the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In yet another exemplary embodiment, the method includes the steps of calculating a mean between the first spread limit and the second spread limit and setting the spread level as the mean if the mean is within the market spread. In still yet another exemplary embodimen t, the method includes the step of identifying a spread amount that is closest to the mean and within the market spread and setting the spread level as the spread amount if the mean is not within the market spread. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and the method includes the steps of determining that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determining that market prices exist tha t are within the overlap determining a mismatch amount in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculating a cross amount for the first security and the second security selecting a crossing price for the first security and the second security that is within the overlap determining that the mismatch amount is available at the crossing price for the second security matching the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices and executing a transaction for the mismatch amount of the second security at the crossing price for the second security. In another exemplary embodiment, the method includes the step of determining that the mismatch amount is available in an external market at the crossing pr ice for the second security. In yet another exemplary embodiment, the method is performed by a financial institution having order inventory and includes the step of determining that the mismatch amount is available in the order inventory at the crossing price for the second security. In still yet another exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and the method includes the step of matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In an exemplary embodiment, the method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of executing a transaction for a first portion of one of the plurality of pair trade requests, described above. In another exemplary embodiment, th e method includes the step of receiving a preference for filling at least some of the plurality of trade requests via the step of matching a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests, described above. Under the present invention, a method for fulfilling a pair trade request is provided and includes the steps of receiving a plurality of pair trade requests and matching at least a portion of one of the plurality of pair trade requests against another of the plurality of pair trade requests. Under the present invention, a system for fulfilling a pair trade request is provided, the system receiving a plurality of pair trade requests and includes a pair trading engine for executing a transaction for a first portion of one of the plurality of pair trade requests The system also includes a pair crossing network for matching a second portion of said one of the plurality of pair trade requests against another of the p lurality of pair trade requests. In an exemplary embodiment, the system includes a link to external markets and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests in the external markets. In another exemplary embodiment, the system includes a financial institution having an order inventory and wherein the pair trading engine executes the transaction for the first portion of one of the plurality of pair trade requests against the order inventory. In yet another exemplary embodiment, the pair trade request includes a first security having a bid price and an ask price and a second security having a bid price and an ask price, and wherein the pair trading engine determines whether the bid price of the first security and the bid price of the second security meet a spread limit determines an amount of the second security that can be sold based on a bid size associated with the second security calculates an equivalent amo unt of the first security that can be bought based on the amount of the second security that can be sold adjusts the equivalent amount of the first security based on adjustment criteria calculates a purchase price for the adjusted equivalent amount of the first security based on the spread limit executes an initiating order to buy said adjusted equivalent amount of the first security at the purchase price and executes a covering order to sell the amount of the second security. In still yet another exemplary embodiment, the pair trading engine executes a covering order to sell the amount of the second security at the bid price of the second security. In an exemplary embodiment, the pair trading engine determines whether the ask price of the first security and the ask price of the second security meet a spread limit determines an amount of the first security that can be bought based on an offer size associated with the first security calculates an equivalent amount of the second security t hat can be sold based on the amount of the second security that can be bought adjusts said equivalent amount of the second security based on adjustment criteria calculates a selling price for the adjusted equivalent amount of the second security based on the spread limit executes an initiating order to sell the adjusted equivalent amount of the second security at the selling price and executes a covering order to purchase the amount of the first security. In another exemplary embodiment, the pair trading engine executes a covering order to purchase the amount of the first security at the ask price of the first security. In yet another exemplary embodiment, the pair trading engine rounds the initiating order to a round lot size. In still yet another exemplary embodiment, the pair trading engine executes a first portion of one of the plurality of pair trade requests in a plurality of tranches. In an exemplary embodiment, the one of the plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit and the another of the plurality of trade requests has a second spread limit and wherein the pair crossing network determines that a range of the first spread limit and the second spread limit overlaps with a market spread sets a spread level calculates prices for the first security and the second security that are within the market spread and based on the spread level and matches the second portion of said one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices. In another exemplary embodiment, the pair crossing network calculates a mean between the first spread limit and the second spread limit and sets the spread level as the mean if the mean is within the market spread. In yet another exemplary embodiment, the pair crossing network identifies a spread amount that is closest to the mean and within the market spread and sets the spread level as the spread amount if the mean is not within the market spread. In still yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests include a first security and a second security, the one of the plurality of pair trade requests has a first spread limit, a buy ratio and a sell ratio, the another of the plurality of trade requests has a second spread limit, a buy ratio and a sell ratio and wherein the pair crossing network determines that the buy ratio and the sell ratio associated with the one of the plurality of trade requests does not equal the buy ratio and the sell ratio of the another of the plurality of trade requests and that an overlap exists between range of the first spread limit and the second spread limit and a market spread determines that market prices exist that are within the overlap determines a mismatch amou nt in the second security based on a difference between the buy ratio and the sell ratio associated with the one of the plurality of trade requests and the buy ratio and the sell ratio of the another of the plurality of trade requests calculates a cross amount for the first security and the second security selects a crossing price for the first security and the second security that is within said overlap determines that the mismatch amount is available at the crossing price for the second security matches the second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests based on the calculated prices and executes a transaction for the mismatch amount of the second security at the crossing price for the second security. In an exemplary embodiment, the pair crossing network determines that the mismatch amount is available in an external market at the crossing price for the second security. In another exemplary embodiment, the pair crossing network determines that the mismatch amount is available in the order inventory at the crossing price for the second security. In yet another exemplary embodiment, the one of said plurality of pair trade requests and the another of the plurality of pair trade requests indicate a number of spreads and wherein the pair crossing network matches a second portion of the one of the plurality of pair trade requests against another of the plurality of pair trade requests if the number of spreads is greater than a minimum number of spreads. In still yet another exemplary embodiment, the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via said pair crossing network, and the system further includes a portfolio manager in communications with the pair crossing network, the portfolio manager receiving the plurality of pair trade requests and routing the at least some pair trade requests to the pair crossing network according to the preference. In an exemplary embodiment, the system includes a pair trading engine for executing at least some of the plurality of pair trade requests, further includes a portfolio manager in communications with the pair trading engine and wherein the plurality of pair trade requests include at least some pair trade requests indicating a preference for execution via the pair trading engine, the portfolio manager receiving the plurality of pair trade requests and routing the at least some of the plurality of trade requests to the pair trading engine according to the preference. Under the present invention, a system for fulfilling a pair trade request is provided, wherein the system receives a plurality of pair trade requests and includes a pair crossing network for matching at least one of the plurality of pair trade requests against another of the plurality of pair trade requests. Accordingly, a method and a system are provided for trading pair securities. The invention accordingly com prises the features of construction, combination of elements and arrangement of parts that will be exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims Other features and advantages of the invention will be apparent from the description, the drawings and the claims. DESCRIPTION OF THE DRAWINGS. For a fuller understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings, in which. FIG 1 is a block diagram of a system for trading securities in pairs according to the present invention. FIG 2 is a flowchart of the steps a pair trading engine included in the system of FIG 1 applies to fill a pair trade request. FIG 3 is a flowchart of the steps a pair crossing network included in the system of FIG 1 applies to fill a pair trade request. FIG 4 is a flowchart of a process by which the pair crossing network of the system of FIG 1 fills imperfectly matched orders and. FIG 5 i s a graph for identifying the market prices for two securities that meet the required spread limits. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS. Referring now to FIG 1 there is shown a block diagram of a system 1 for trading securities in pairs according to the present invention System 1 receives pair trade requests from clients operating client access devices 7 and attempts to fill the pair trade requests according to the parameters associated with the particular pair trade request System 1 includes two different subsystems for filling pair trade requests a pair trading engine 3 and a pair crossing network 5 As will be described below, pair trading engine 3 receives a pair trade request and attempts to fill in whole or in part the trade request by executing the appropriate trades in an external market 13 that may include, by way of non-limiting example, the New York Stock Exchange, the NASDAQ or any other financial market Pair trading engine 3 may also fill in whole or in part a pair trade request by executing a transaction against order inventory 11 of non-pair trade requests controlled by the financial institution that is operating system 1 In addition, pair trading engine may also fill in whole or in part a pair trade request by forwarding the trade request to pair crossing network 5 for matching with other pair trade requests. Likewise, pair crossing network 5 receives a pair trade request and fulfills in whole or in part the request by matching it against another pair trade request received by pair crossing network 5 by matching the request against inventory 11 controlled by the financial institution and or by forwarding the trade request to pair trading engine 3 for execution in external markets 13.System 1 also includes a portfolio manager 9 that may be, for example, a software program executing on a computer system that receives the pair trade requests from client access device 7 and presents the trade request to either pair trading engine 3 pair crossi ng network 5 or both, depending on the trade parameters set by the client Also, the client may query portfolio manager 9 regarding the status of any pair trade request the client has presented to system 1.In operation, system 1 may fulfill a pair trade request either using pair trading engine 3 or pair crossing network 5 or a combination of the two For example, a pair trade request received by system 1 may be completely filled by pair trading engine 3 as follows. Assume a case where XYZ is taking over ABC and is offering 0 575 shares of XYZ for each ABC share and investor Arb wants to invest in the price difference between ABC stock and XYZ stock To take advantage of the price difference, Arb wants to lock in the difference between the value offered 0 575 XYZ stock and the value of ABC stock by buying ABC stock and selling XYZ stock subject to the condition that ABC 0 575 XYZ 1 19 i e Arb desires to capture a 1 19 difference between XYZ s takeover offer and ABC s share price. In order to fill this pair trade, Arb presents a pair trade request to portfolio manager 9 using client access device 7 The pair trade request typically includes a number of parameters that define the pair trade and that also may be used by portfolio manager 9 in determining how the pair trade request is to be filled Arb typically indicates in the trade request the number of spreads the Arb desires to invest in and also provides a minimum and maximum share amount that he is willing to trade per tranche. For example, Arb may indicate a desire to invest in 100,000 spreads and may only wish to trade the spread 3,000-8,000 shares at a time Arb generally sets this tranche size range based on the liquidity and volatility of ABC stock and XYZ stock Arb may set a larger minimum tranche size if ABC stock and XYZ stock are fairly liquid stocks because higher liquidity increases the likelihood that a larger tranche size will be executed Arb may set a lower maximum tranche size if XYZ stock and ABC stock are volatile stocks so as to limit the leg risk associated with executing a pair trade. Yet another pair trade parameter Arb provides is the spread limit in the above case 1 19 which is the amount Arb desires to capture in the trade Arb does not have to provide, however, the discrete prices at which trades for ABC and XYZ stock are to be executed as these prices are calculated by pair trading engine 3 and or pair crossing network 5 , as will be described below. Referring now to FIG 2 there is shown a flowchart describing the steps pair trading engine 3 applies to fill a pair trade request The flowchart in FIG 2 is based on the above example and the market data listed in Table 1 below. Initially, in Step 201 pair trading engine 3 determines whether the bid bid prices or ask ask prices of ABC and XYZ stock, respectively, meet the spread limit requirement of the particular pair trade request In this case the bid bid spread is 1 4375 122 50 0 575 69 and the ask ask spread is 1 1969 122 625 0 575 69 3125 so that each spread is less than the spread limit of 1 19, as is required for this particular trade Once it is determined that either the bid bid spread or the ask ask spread meets the spread limit, then in Step 202 it is determined as is indicated in Table 1 how much XYZ stock can be sold at the bid and how much ABC stock can be bought at the ask In an exemplary embodiment, the client may specify whether the bid bid spread, the ask ask spread or either the bid bid or the ask ask spread must exceed the indicated spread limit for a transaction to proceed If neither the bid bid spread nor the ask ask spread meets the spread limit, the process waits a period of time for example 0 10 seconds and returns to Step 201 to again test whether the bid bid spread or the ask ask spread meets the spread limit. Next, in step 203 an equivalent amount of stock that can be sent into the market i e bought sold in the market is calculated for a spread based on the bid bid price spread and or the as k ask price spread that meets the spread limit In this example, if a maximum of 10,000 shares of XYZ stock can be sold into the market i e the XYZ bid size then, based on the ABC XYZ ratio of 1 0 575 in this case , a total of 17,391 10,000 0 575 shares of ABC stock are to be bought in order to execute a balanced pair trade Likewise, if a maximum of 1,500 shares of ABC stock can be bought in the market i e the ABC ask size , then, based on the ABC XYZ ratio of 1 0 575 in this case , a total of 863 1500 0 575 shares of XYZ stock are to be sold in order to execute a balanced pair trade. Next, in Step 204 the pair trade share amounts calculated in Step 203 are adjusted to conform to the wave maximum and minimum parameters i e the maximum minimum tranche size included in the pair trade request as well as market round lot limits In the above example, the amount of ABC shares to be bought that was calculated based on the XYZ bid size i e 17,391 is first rounded to an even lot size i e 17,400 a nd then reduced to the maximum tranche size of 8000 Also, the amount of XYZ shares to be offered that was calculated based on the ABC ask size i e 863 is first rounded to an even lot size i e 900 and then increased to 1,700 shares to meet the minimum tranche size of 3000 3000 0 575 1777 In an exemplary embodiment the minimum and maximum tranche size is scaled by the particular ratio for example, in the above case, the tranche sizes for XYZ stock is scaled by 0 575 In another embodiment, the maximum minimum tranche size is used for each security in the pair trade request without scaling In yet another exemplary embodiment, the pair trade request includes a separate maximum minimum tranche for each security. Once the share amounts for the pair trade are calculated, in Step 205 the share prices that are needed to meet the spread limit of the pair trade request are calculated For example, for a pair trade based on the bid bid price spread, in order to meet the spread limit of 1 19 credit, t he price at which ABC stock is to be bid should be no greater than 69 2475 122 50 0 575 1 19 a share Likewise, for a pair trade based on the ask ask price spread, in order to meet the spread limit, the price at which XYZ stock is to be offered should be greater than or equal to 122 6130 69 3125 1 19 0 575 a share. Next, once the pair trade share amounts and share prices have been calculated, in Step 206 pair trading engine 3 sends initiating orders to external markets 13 in order to fill the pair trade request The initiating orders may include an initiating order for executing a pair trade based on the bid bid spread in this case a bid for 8,000 shares of ABC stock at 69 2475 and or an initiating order for executing a pair trade based on the ask ask spread in this case an offer of 1,700 shares of XYZ stock at 122 6130.Finally, as the initiating orders sent to external markets 13 in Step 207 get filled, pair trading engine 3 automatically sends into the market the covering side of the pa ir trade So, for example, as the initiating order of buying 8,000 shares of ABC stock at 69 2475 gets filled, pair trading engine 3 sends an order to external markets 13 to sell 4,600 8,000 0 575 shares of XYZ stock at 122 50.In an exemplary embodiment, the client s pair trade request includes threshold amounts that indicate the amount of variance in stock price and or share amount the client is willing to absorb For example, if in the process of covering the initiating order the price of XYZ stock dips to 122 49 in which case the spread limit of the pair trade would drop to 1 18 , then pair trading engine 3 would still sell XYZ stock at the price of 122 49 if the 0 01 difference was within the threshold amount included in the pair trade request Similarly, the pair trade request may include threshold amounts for any other pair trade parameter, including by way of non-limiting example, the number of spreads to be purchased and the tranche sizes If, however, a particular threshold amount indicated by the client is exceeded for any given pair trade parameter, then pair trading engine 3 would attempt to cancel the initiating order and or the covering order that may be possible if the orders have not yet reached the market or have not yet been filled In such a case, pair trading engine 3 would then repeat the above analysis for determining suitable initiating and cover orders. To fill a pair trade request, pair trading engine 3 executes trades utilizing the method described above Typically, pair trading engine 3 tranches a pair trade request and trades piece-meal in external markets 13 In certain cases, however, it may be difficult to fill a trade request by executing several transactions in external markets 13 either because the pair trade request is for a very large number of spreads or includes stocks that are illiquid in which cases pair trading engine 3 may be ineffective in filling the pair trade request Also, in certain situations, a client wishing to remain anonym ous may indicate in the pair trade request a preference that no orders be sent to external markets 13 In these circumstances, portfolio manager 9 may route the particular pair trade request to pair crossing network 5.Referring now to FIG 3 there is shown a flowchart illustrating the steps pair crossing network 5 applies to fill a pair trade request The flowchart in FIG 3 is based on the above example and the market data listed in Table 2 below. Spread Limit as defined by 0 575 XYZ ABC. Continuing the previous example, assume the pair trade request issued by Arb for 100,000 spreads was half-filled by pair trading engine 3 Also, assume that system 1 receives a pair trade request from Antiarb that indicates a desire to sell 30,000 shares of ABC and buy 17,200 shares a ratio of 1 0 575 and also indicates a spread limit of 1 30 i e ABC 0 575XYZ 1 30 In this case Arb and Antiarb s orders are complimentary in the primary order elements securities, ratios and buy versus sell Also, Antiarb is willing to pay 0 11 per spread more than Arb is demanding from the marketplace Based on these parameters, there is an opportunity for Arb s and Antiarb s trade requests to be filled via pair crossing network 5.If Antiarb s pair trade request was marked for trading by pair trading engine 3 then portfolio manager 9 sends Antiarb s order to pair trading engine 3 for execution Pair trading engine 3 then sends the parameters of Antiarb s trade request, as well as all orders waiting for execution in pair trading engine 3 to pair crossing network 5 Pair crossing network 5 will recognize as described above that there is a crossing opportunity between Arb s order and Antiarb s order In this case, pair crossing network 5 then directs pair trading engine 3 to suspend the execution of Antiarb s order in the amount that can be crossed by pair crossing network 5 30,000 spreads in this case In addition, pair trading engine 3 routes a cross amount of 30,000 spreads from Arb s order to pair crossing network 5 for crossing against Antiarb s order At this point, the pair crossing network 5 crosses the Antiarb order against a portion of Arb s order, as follows. Assume the prevailing market conditions at the time of the cross are as shown in Table 3 Furthermore, Table 3 indicates the XYZ Ratio-Adjusted Value for both the bid and ask prices based on the conversion ratio of 1 0 575 Based on the XYZ Ratio-Adjusted Values, a Bid Ask Spread Range i e the spread provided for a cross between the bid price of ABC stock and the XYZ Ratio-Adjusted ask price of 1 3863 is calculated and an Ask Bid Spread Range i e the spread provided for a cross between the ask price of ABC stock and the XYZ Ratio-Adjusted bid price of 1 05 is calculated. To perform the cross, in Step 301 pair crossing network 5 first determines whether the range of spread limits associated with Arb s and Antiarb s trade requests i e 1 30- 1 19 coincides with the range of the prevailing market spread 1 3863- 1 05 In this example, the range of spread limits does coincide with the prevailing market spread because at least a portion of the spread limit range overlaps with a portion of the market spread Thus, a cross can occur. Next, in Step 302 pair crossing network 5 calculates the mean of Arb s and Antiarb s spread order limit which is 1 30 1 19 2 1 245 and determines whether the mean is within the range of the market spread i e 1 3863- 1 05 If it is, then in Step 303 pair cros sing network 5 calculates the prices at which to cross The prices must be within the current markets for ABC stock and XYZ stock, and satisfy market uptick requirements for short sales , and provide a spread that is equal to the spread level calculated above For example, with the inside market for ABC stock at 70 00-70 25 and the inside market for XYZ stock at 124 00-124 15, a cross price of 70 11 for ABC stock and 124 096 for XYZ stock provides the spread of 1 2452 thereby meeting the requirement of both Arb s and Antiarb s trade request Finally, in Step 304 pair crossing network 5 crosses 30,000 shares of ABC stock at 70 11 with Arb buying and Antiarb selling and 17,200 shares of XYZ at 124 096 with Arb selling and Antiarb buying. If it is determined in Step 302 that the mean of Arb s and Antiarb s spread order limits does not fall within the range of the market spread, then in Step 305 the spread closest to the mean of the two spread limits that is also within the market spread is ca lculated For example, if the market spread is 1 3863- 1 28, then the mean of the two spread limits 1 245 is not within the market spread In such a case, 1 28 is selected as the spread level that is closest to the mean and within the market spread In an exemplary embodiment, the spread level at which Arb and Antiarb cross can be determined in any other suitable manner as long as the spread level is within the market spread and within the range of spread limits indicated in the pair trade requests. Once the spread level is determined, the method proceeds to Step 303 in which pair crossing network 5 calculates prices to cross at that are within the current markets for ABC stock and XYZ stock and that meet the calculated spread level In the case where the calculated spread level is 1 28, the cross will occur at a price of 70 08 for ABC stock and 124 1043 for XYZ stock Finally, the method proceeds to Step 304 in which pair crossing network 5 performs the cross between Arb and Antiarb. Once a pair trade request is filled or partially filled , the transaction details are reported to portfolio manager 9 and made available to the client operating client access device 7.In the previous example, pair crossing network 5 crosses orders in which both Arb and Antiarb desire to trade the same pair of securities in the same ratio In an exemplary embodiment, pair crossing network 5 executes a cross between two pair trade requests that are not perfectly matched. For example, assume that pair crossing network 5 receives the pair trade requests as shown in Table 4 Note that these two pair trade requests are imperfectly matched because each trade request uses a different ratio between ABC and XYZ stock. Arb s Spread Limit is defined by 0 575 XYZ ABC Antiarb s Spread Limit is defined by 0 6 XYZ ABC. Also, assume the market in ABC and XYZ stocks at the time the pair trade requests are received by pair crossing network 5 is as described in Table 5 below. Arb s XYZ Ratio-Adjusted Value. Arb s Dollar Range. AntiArb s XYZ Ratio-Adjusted Value. AntiArb s Dollar Range. Referring now to FIG 4 there is shown a flowchart illustrating a process by which pair crossing network 5 fills these imperfectly matched order First, in Step 401 pair crossing network 5 determines whether Arb s buy security equals Antiarb s sell security and whether Arb s sell security equals Antiarb s buy security If both conditions are not met, then a cross between the two orders cannot occur If the two conditions are met, then in Step 402 it is determined whether Arb s buy ratio equals Antiarb s sell ratio and whether Arb s sell ratio equals Antiarb s buy ratio If these ratios are the same, then pair crossing network 5 proceeds t o cross the two orders as described in the example above Note that for a cross to occur at this stage does not require the ratios themselves to match but rather that the ratios of the ratios match for e g a ratio of 2 3 matches a ratio of 0 667 1.If, however, the two ratios are not equal as in this case where Arb s sell ratio does not equal Antiarb s buy ratio , then in Step 403 pair crossing network determines whether there is an overlap between Arb s and Antiarb s spread limit that also falls within the bid ask market for ABC and XYZ stock To make such a determination, pair crossing network 5 calculates whether there are market prices for both ABC and XYZ stock that satisfy the following inequalities L 1 Ratio A ABC Ratio B XYZ and 1 L 2 Ratio C ABC Ratio D XYZ 2 Where L 1 is Arb s spread limit of 1 19 credit, L 2 is Antiarb s spread limit of 4 40 debit, RatioA is Arb s buy ratio of 1 1, RatioB is Arb s sell ratio of 1 0 575, RatioC is Antiarb s sell ratio of 1 1 and RatioD is Antiar b s buy ratio of 1 0 6.Referring now to FIG 5 there is shown a graph 51 that depicts market prices for ABC and XYZ stock that meet the spread limits of Arb and Antiarb In graph 51 the x-axis represents the prices for XYZ stock while the y-axis represents the prices for ABC stock Graph 51 includes a shaded area 53 that is the universe of market prices for ABC and XYZ stock that could satisfy the spread trade involving those stocks Also included in graph 53 is a spread limit line L 1 inequality 1 , above that represents the spread limit associated with Arb and a spread limit line L 2 inequality 2 , above that represents the spread limit associated with Antiarb Thus, the solution set of market prices that satisfies inequalities 1 and 2 is the portion of dark shared area 53 that falls between spread limit line L 1 and spread limit line L 2 In this example, a cross at a share price for ABC of 70 14 and a share price of 124 15 for XYZ stock meets the investor s spread limits and falls within the market prices for ABC and XYZ stock. If it is determined that no share prices for both ABC and XYZ stock satisfy Arb s and Antiarb s spread limits, then no cross can occur If such share prices do exist, then in Step 404 it is determined which of the investors desires to transact in fewer shares of ABC stock and a mismatch in share amounts caused by the differing ratios is determined In our example, Antiarb desires to sell fewer ABC shares than Arb desires to buy 30,000 vs 50,000 Then, in Step 405 pair crossing network 5 determines the number of XYZ shares that can be crossed between Arb and Antiarb based on the maximum amount of ABC shares that can be crossed 30,000 in this example Based on the Antiarb ABC order quantity of 30,000 shares, the maximum number of XYZ shares that Arb will cross with Antiarb is.30 000 Arb XYZ Ratio Arb ABC Ratio 30 000 0 575 1 17 300 17 250 rounded to an even lotsize. While the maximum quantity of XYZ shares that Arb will cross is 17,300, Antiarb s trade request indicates a desire to cross 18,000 shares To overcome this imbalance, in Step 406 pair crossing network 5 is in communications with external markets 13 for determining whether the excess 700 XYZ shares needed to satisfy Antiarb s trade request can be transacted for in external markets 13 In an exemplary embodiment, pair crossing network 5 makes this determination by issuing a query to pair trading engine 3 as to whether 700 shares of XYZ stock can be bought in external markets 13 Because, as indicated in Table 5, 3,000 shares of XYZ stock are offered at 124 15, pair trading engine 3 responds to pair crossing network 5 that the 700 shares needed to balance the cross between Arb and Antiarb are available from external markets 13 at 124 15.Next, in Step 407 pair crossing network calculates the cross prices that are necessary such that Arb and Antiarb achieve their respective spread limits while also incorporating the excess 700 shares of XYZ stock that must be purchased from exte rnal markets 13 at 124 15 to satisfy Antiarb s trade request An example of such cross prices that meet these criteria is a price of 70 14 for ABC stock and a price of 124 15 for XYZ stock. Once the cross prices are calculated, in Step 408 pair crossing network 5 crosses 30,000 shares of ABC stock and 17,300 shares of XYZ stock between Arb and Antiarb and also buys 700 shares of XYZ stock at 124 15 in external markets 13 on behalf of Antiarb Thus, both Arb and Antiarb s pair trade requests are satisfied. Alternatively, the entire 18,000 shares of XYZ stock may be crossed thereby fully satisfying Antiarb s trade request In such a case, the ratio mismatch is addressed by Arb purchasing an additional 1200 700 0 575 rounded to a lotsize shares of ABC stock from external market 13 or from firm inventory 11.Once the trade is completed, the details of the transaction are provided to portfolio manager 9 to report the transaction details to the investors. In an exemplary embodiment, a pair order or portion thereof may be filled against an internal inventory 11 of trade requests maintained by the financial institution operating system 1 For example, in the previous example in which an excess of 700 shares of XYZ stock needs to be purchased in order for a match i e cross between Arb and Antiarb s trade requests to occur, instead of determining whether the 700 shares are available in external markets 3 pair crossing network 5 examines firm inventory 11 to determine whether the shares are available at the required price Likewise, in cases where pair trading engine 3 desires to execute a pair trade based on orders to be sent to external markets 13 pair trading engine 3 may first determine whether the order can be filled, in whole or in part, using trade requests pending in firm inventory 11 Generally, the advantages of filling an order using pending trade requests in firm inventory 11 is that execution is faster, transaction costs are lower and leg risk is minimized. In another exempl ary embodiment, a client s pair trade request may also include a minimum number of spreads that can be traded in pair crossing network 5 Also, pair crossing network 5 may be designed to require a minimum share amount for a cross to occur A minimum number of spreads that can be traded may be provided in order to reduce the distractions and booking costs associated with numerous smaller trades that may exceed the benefits of a de minimis fill. In another exemplary embodiment, portfolio manager 9 publishes the inside cross market for any pair that a client has selected for crossing in pair crossing network 5 In still another exemplary embodiment, the client has the option for each pair trade selected for crossing in pair crossing network 5 to designate that the order should be reflected in the published inside cross market This inside cross market consists of the tightest spread bid and offer and corresponding bid size and offer size from all client pair orders pending in pair crossing net work 5 In this way, a client can assess the likelihood and timing of a pair trade request being filled by pair crossing network 5 Also, by publishing the client s spread interest, others seeking liquidity can trade at the client s level. In an exemplary embodiment, the client can designate each pair order designated for pair trading engine 3 and or pair crossing network 5 for Broker Negotiation If Broker Negotiation is designated, the client s broker-dealer sales representative is notified of the client s spread order thereby prompting the broker-dealer to solicit a complementary, agency order from another client The client may also designate each pair order for Broker Facilitation in which case the client allows the broker-dealer to act principally to fill the client s order. In summary, the advantages to a client of using pair trading engine 3 is that pair trading engine 3 allows the client to trade a spread order while limiting leg risk or the risk of missing a targeted spread level T his is accomplished by breaking the total order into tranches of sizes proportionate to the market, subject to user minimums and maximums, that can be traded in external markets 13 or against firm inventory 11 Orders executed via pair trading engine 3 however, are typically of a lower traded volume because trading is constrained to the liquidity available in the market In contrast, trades executed via pair crossing network 5 are not constrained by market liquidity and do not have to be tranched to minimize leg risk In particular, the benefits of filling a pair trade request via pair crossing network 5 are as follows. Elimination of Leg Risk Pair crossing network 5 potentially provides a deeper well of liquidity because the trades are brokered, as a spread, directly between spread investors via a central clearing facility Moreover, the introduction and use of a pair trading facility eliminates the leg risk described above without a sacrifice of liquidity. Large Transactions Only Certain l arge investors may prefer to use pair crossing network 5 rather than pair trading engine 3 to avoid having a trade request broken up into numerous small executions For example, sudden, brief moves in one of the two stocks included in the pair trade request may cause pair trading engine 3 to issue numerous small executions to fill the request While a small investor may welcome capturing these small opportunities, a large investor may find such small executions to be more of a nuisance than a service. Price Setting versus Price Taking Large investors seeking liquidity may prefer to set their price via the pair crossing network 5 Also, other spread investors looking for liquidity can use pair crossing network 5 to monitor and trade with the large investor at the large investor s level While client orders directed to pair trading engine 3 can designate a spread limit, such orders are essentially price-takers as the market reaches the desired level, the orders are executed Moreover, the pair trading engine tranching mechanism creates relatively small orders, allowing institutional flows to move the individual stocks As a result, the small, tranched orders generated by pair trading engine 3 can become overpowered by single-name institutional flows In addition, orders designated solely for pair trading engine 3 and not for pair crossing network 5 are not published to a central quote facility such as by portfolio manager 9 thereby preventing other spread traders from knowing the size and limit of a pair trading engine order. Illiquid Stocks vs Liquid Stocks Spreads that include one or two illiquid stocks are difficult to fill using pair trading engine 3 alone Because illiquid stocks often demonstrate small bid and ask sizes and wide bid-ask spreads, pair trading engine 3 will typically only issue market orders having small quantities subject to user minimums and maximums that presents the client with greater leg risk from mid-trade changes in the bid-ask prices In contrast, o rders routed to price crossing network 5 are not confined by liquidity in the market place thereby allowing large crosses between spread traders in illiquid spreads. Accordingly, a system and method for trading pair securities is provided in which the client receives the benefits of having a pair order filled by either pair trading engine 3 pair crossing network 5 or a combination of both. A number of embodiments of the present invention have been described Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention Based on the above description, it will be obvious to one of ordinary skill to implement the system and methods of the present invention in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device Each computer program may be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired and in any case, the language may be a compiled or interpreted language Suitable processors include, by way of example, both general and special purpose microprocessors Furthermore, alternate embodiments of the invention that implement the system in hardware, firmware or a combination of both hardware and software, as well as distributing modules and or data in a different fashion will be apparent to those skilled in the art and are also within the scope of the invention In addition, it will be obvious to one of ordinary skill to use a conventional database management system such as, by way of non-limiting example, Sybase, Oracle and DB2, as a platform for implementing the present invention Also, network access devices can comprise a personal computer executing an operating system such as Microsoft Windows , Unix , or Apple Mac OS , as well as software applications, such as a JAVA program or a web browser Access devices can also be a terminal device, a palm-type computer, mobile WEB access device or other device that can adhere to a point-to-point or network communication protocol such as the Internet protocol Computers and network access devices can include a processor, RAM and or ROM memory, a display capability, an input device and hard disk or other relatively permanent storage Accordingly, other embodiments are within the scope of the following claims. It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above process, in a described product, and in the construction set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description shown in the accompanying drawing shall b e interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.

Corretor Forex Três Lagoas

Thursday 20 July 2017

Par Trading System And Method

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