The U.S. housing boom during the first part of the past decade was marked by rapid house price appreciation and greater access to mortgage credit for lower credit-rated borrowers. The subsequent collapse of the housing market and the high default rates on residential mortgages raise the issue of whether the pace of house price appreciation and the mix of borrowers may have affected the influence of fundamentals in housing and mortgage markets. This paper examines that issue in connection with one aspect of mortgage financing, the choice among fixed-rate and adjustable-rate mortgages. This analysis is motivated in part by the increased use of adjustable-rate mortgage financing, notably among lower credit-rated borrowers, during the peak of the housing boom. Based on analysis of a large sample of loan level data, we find strong evidence that house price appreciation dampened the influence of a number of fundamentals (mortgage pricing terms and other interest rate related metrics) that previous research finds to be important determinants of mortgage financing choices. With regard to the mix of borrowers, the evidence indicates that, while low risk-rated borrowers were affected on the margin more by house price appreciation, on balance those borrowers tended be at least as responsive to fundamentals as high risk rated borrowers. The higher propensity of low credit-rated borrowers to choose adjustable-rate financing compared with high credit-rated borrowers in the housing boom appears to have been related to borrower credit risk metrics. Given the evidence related to loan pricing terms, other interest rate metrics and fixed effects, the relation of credit risk to mortgage financing choice seems more consistent with considerations such as credit constraints, risk preferences, and mortgage tenor than just a systematic lack of financial sophistication among higher credit risk borrowers.
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