For the past several years, the news media have carried countless stories about soaring defaults among subprime mortgage borrowers. Although concern over this segment of the mortgage market is certainly justified, subprime mortgages only account for about onequarter of the total outstanding mortgages in the United States. The remaining 75 percent are prime loans that are made to borrowers with good credit, who fully document their income and make traditional down payments. While default rates on prime loans are significantly lower than those on subprime loans, they are also increasing rapidly. For example, among prime loans made in 2005, 2.2 percent were 60 days or more overdue 12 months after the loan was made (our definition of default). For loans made in 2006, this percentage nearly doubled to 4.2 percent, and for loans made in 2007 it rose by another 20 percent, reaching 4.8 percent. By comparison, the percentage of subprime loans that had defaulted after 12 months was 14.6 percent for loans made in 2005, 20.5 percent for loans made in 2006, and 21.9 percent for loans made in 2007. To put these figures in perspective, only 1.4 percent of prime loans and less than 7 percent of subprime originated in 2002 defaulted within their first 12 months.1 How do we account for these historically high default rates? How have recent trends in home prices and economic conditions affected mortgage markets? One of the things we want to consider, specifically, is whether prime and subprime loans responded similarly to home price dynamics.