Some truths about ostriches: Who doesn't prepay their mortgages and why they don't

Prepayment estimation is essential in forecasting expected mortgage cash flow patterns. Accordingly mortgage and mortgage-backed security prices are highly dependent on prepayment assumptions. Yet borrower prepayment behavior appears to be highly irrational, in the sense that many borrowers prepay their mortgages when it is not optimal to do so and fail to prepay their mortgages when the prepayment option is substantially in the money. In this paper, we explore the latter phenomenon, using a large data set of loans originated during the relatively high-rate 1980s that have failed to prepay by year-end 1996. As a control group, we examine similar loans that did prepay during the refinancing boom of 1993. By coupling Case-Shiller house price index information at the zip-code level, we can analyze the effect of broader housing market trends, especially housing appreciation, on borrower prepayment behavior. Although housing prices did decline significantly during the late 1980s and early 1990s in many areas;of the United States, we find evidence that only about 25% of non-refinancing households might have been constrained by declining collateral values. Household demographic characteristics may provide some further explanation for this apparently non-optimizing behavior; however, we do not have a complete explanation. (C) 1999 Academic Press.