The Complexities of Mortgage Options (Prendergast)
Mortgage option prices behave quite differently than the prices of
options on underlying securities that do not exhibit significant
convexity. As a result, the intuition of many market participants
about option risk characteristics does not typically apply to
mortgage options.
The risk characteristics of these options: negative convexity of
the underlying mortgage and the positive gamma of the option
impact call option convexity in opposing directions. As a result,
call option convexity can be either positive or negative,
depending on the interest rate scenario and option specification.
On the other hand, a mortgage put option is always positively convex.
A quantitative understanding of these risk characteristics is critical
for money managers and broker/dealers who use mortgage options.
The Complexities of Mortgage Options
Prendergast, Joseph R.
THE JOURNAL OF FIXED INCOME
March 2003