In recent years, interest-rate-contingent claims such
as caps, swaptions, bond options, captions, and mortgage-
backed securities have become increasingly
popular. The valuation of these instruments is now a
major concern of both practitioners and academics.
Practitioners have tended to use different models
for valuing different interest-rate-derivative securities.
For example, when valuing caps, they frequently
assume that the forward interest rate is lognormal and
use Black’s (1976) model for valuing options on commodity
futures, The volatility of the forward rate is
assumed to be a decreasing function of the time to
maturity of the forward contract. When valuing Euro-