Another feature of mortgage contracts is the
use of debt and leverage
Default risk increases
with debt relative to a house’s price,
or the
loan-to-value ratio.
The probability of
default is close to zero
below
80 percent
a rationale for why this threshold
is used as a requirement for borrowers to purchase
additional mortgage insurance
Above
80 percent, the probability of default and its
severity are convex in the LTV