The market for U.S. Treasury securities is a marvel of modern finance. In 2009 the Treasury auctioned $8.2 trillion of new securities, ranging from 4-day bills to 30-year bonds, in 283 offerings on 171 different days. By contrast, in the decade before World War I, there was only about $1 billion...

In 1973, Fischer Black, Myron Scholes, and Robert Merton pointed out that securities issued by a corporation can be priced as claims whose values are contingent on the value of the enterprise as a whole. The notion of treating corporate securities as contingent claims is intrinsically important,...