Valuing the implicit guarantee of the Federal National Mortgage Association

The paper analyzes the guarantee of the Federal National Mortgage Association (FNMA). Rather than try to price the guarantee, we used time-series estimates of its value from Kane and Foster to infer the behavior of FNMA in exploiting the guarantee. The results are consistent with a model that predicts that FNMA does not take as much risk as it might. Rather, it trades off risk and return, but it does increase risk and exploit the guarantee when it gets in trouble (as it did in 1981).We have received helpful research assistance from Peter Carr and Bruno Gerard.