  In general, homeowners refinance in response to a decrease in interest rates,
as their borrowing costs are lowered. However, it is worth investigating the
effects of refinancing after taking the underlying costs into consideration.
Here we develop a synthetic mortgage calculator that sufficiently accounts for
such costs and the implications on new monthly payments. To confirm the
accuracy of the calculator, we simulate the effects of refinancing over 15 and
30 year periods. We then model the effects of refinancing as risk to the issuer
of the mortgage, as there is negative duration associated with shifts in the
interest rate. Furthermore, we investigate the effects on the swap market as
well as the treasury bond market. We model stochastic interest rates using the
Vasicek model.
