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The dramatic government takeover of Fannie Mae and Freddie Mac in September, 2008 was motivated in part by a desire to ensure a continued flow of credit to the mortgage market. This study examines a closely related issue: the extent to which GSE activity crowds out mortgage purchases by private secondary market intermediaries. Evidence of substantial crowd out suggests that government support for the GSEs may be less warranted, whereas the absence of crowd out implies that GSE loan purchases enhance liquidity.

Using 1994-2008 HMDA data for conventional, conforming sized loans, three distinct periods with regard to GSE crowd out are apparent. From 1994-2003, the share of loans sold to the secondary market increased from 60 to over 90 percent, private sector and GSE market shares of loan purchases were roughly similar for most market segments, and IV estimates indicate relatively little GSE crowd out of private secondary market purchases. From 2004 to 2006, private loan purchases boomed and dominated those of the GSEs, while IV estimates indicate crowd out jumped to 50 percent at the peak of the boom. This is especially true in the market for home purchase as opposed to refinance loans. With the crash in housing and mortgage markets in 2007, private sector intermediaries pulled back, the GSEs regained market share, and evidence of GSE crowd out disappeared in both the home purchase loan and refinance markets. These patterns suggest that the degree of GSE crowd out varies with market conditions and that the federal takeover of Fannie Mae and Freddie Mac likely served to enhance liquidity to the mortgage market during the 2007-2009 financial crisis.

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