Did affordable housing mandates cause the subprime mortgage crisis?

The 1992 Federal Housing Enterprises Financial Safety and Soundness Act (GSE Act) mandated that a specified percentage of Fannie Mae and Freddie Mac purchases come from underserved populations. A number of prominent observers have pointed to the GSE Act as a root cause of the recent housing crisis. This paper evaluates the link between the GSE Act and relaxed mortgage market standards. Using loan application-level data from the Home Mortgage Disclosure Act, I analyze whether the GSE Act's single-family affordable housing goals altered mortgage lending or purchasing decisions. To identify this effect, I use a regression discontinuity design that exploits arbitrary cutoffs used to determine whether a loan satisfies the GSE Act goals. I find that the GSE Act's single-family affordable housing goals increased GSE purchases from very low-income borrowers by 4.4% but had no effect on mortgage lending. These results stand up to a number of specification and robustness checks.