William W. Toy ("Bill") is a leading finance practitioner in the area of equity derivatives, and a pioneering modeller in the area of interest rate derivatives. He is best known as a co-developer of the Black–Derman–Toy short rate model, widely used for interest rate and bond options. His roles have included managing director and head of US Equity Derivatives at CDC Capital, Inc. in New York City, a subsidiary of Caisse des dépôts et consignations, and Vice President in Goldman Sachs' equity derivatives department. He earned his S.B., S.M. and Ph.D. (1978; experimental elementary particle physics) at MIT.