This paper argues that econometric analysis of housing price indexes before 2006 generated forecasts of future long-term price growth and low estimated probabilities of extreme price decreases. These forecasts of future increases in home-loan collateral values may have affected both the demand and the supply of mortgages. Standard time series models using repeat-sales indexes suggest that positive trends had a long half-life. Expectations based on such models could lead to an asset bubble. Analysis of data from the HMDA loan database and LoanPerformance.com at the MSA level and at the loan level substantiates the effects of past price trends on the demand and supply of subprime mortgages. On the demand side, at the MSA level, past home price increases are associated with more subprime applications, higher loan to income ratios and lower loan to value ratios of applications for both prime and subprime mortgages. This is consistent with the notion that households not only borrowed more but also invested more in home equity conditional on greater past house price increases. On the supply side, past home price appreciation had a significantly greater impact on the approval rate of subprime applications than the approval rate of prime applications. Loan level analysis indicates that past home price appreciation increased the approval rate of subprime applications but did not affect the approval rate of prime applications. Further, approved HMDA subprime loans had higher loan to income ratios in MSAs with greater past house price trends.

This paper argues that econometric analysis of housing price indexes before 2006 generated forecasts of future long-term price growth and low estimated probabilities of extreme price decreases. These forecasts of future increases in home-loan collateral values may have affected both the demand and the supply of mortgages. Standard time series models using repeat-sales indices suggested that positive trends had a long half-life. Expectations based on such models supported expectations that could lead to an asset bubble.Analysis of data from the HMDA loan data base and LoanPerformance.com at the MSA level and at the loan level substantiates both supply and demand effects of past price trends in housing markets, particularly with respect to subprime mortgage applications and approvals. At the MSA level, past home price increases are associated with higher subprime applications and loan to value ratios. Approval probability of subprime loans was not affected by higher loan to value ratios. At the loan level, the approval probability of subprime applications is also positively associated with past home price appreciation. These results differ for prime mortgages.

Thanks to Justin Haaheim for research support. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Economic Research. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

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