'Research by Edward Pinto, a former chief credit officer of Fannie has shown that 27 million loans—half of all mortgages in the U.S.—were subprime or otherwise weak by 2008. That is, the loans were made to borrowers with blemished credit, or were loans with no or low down payments, no documentation, or required only interest payments.
Of these, over 70% were held or guaranteed by Fannie and Freddie or some other government agency or government-regulated institution. Thus it is clear where the demand for these deficient mortgages came from.'
'Beginning in 1992, the government required Fannie Mae and Freddie Mac to direct a substantial portion of their mortgage financing to borrowers who were at or below the median income in their communities. The original legislative quota was 30%. But the Department of Housing and Urban Development was given authority to adjust it, and through the Bill Clinton and George W. Bush administrations HUD raised the quota to 50% by 2000 and 55% by 2007.'
'As housing bubbles grow, rising prices suppress delinquencies and defaults. People who could not meet their mortgage obligations could refinance or sell, because their houses were now worth more.
Accordingly, by the mid-2000s, investors had begun to notice that securities based on subprime mortgages were producing the high yields, but not showing the large number of defaults, that are usually associated with subprime loans. This triggered strong investor demand for these securities, causing the growth of the first significant private market for MBS based on subprime and other risky mortgages….
When the bubble deflated in 2007, an unprecedented number of weak mortgages went into default, driving down housing prices throughout the U.S. and throwing Fannie and Freddie into insolvency. Seeing these sudden losses, investors fled from the market for privately issued MBS, and mark-to-market accounting required banks and others to write down the value of their mortgage-backed assets to the distress levels in a market that now had few buyers. This raised questions about the solvency and liquidity of the largest financial institutions and began a period of great investor anxiety.'