This excerpt taken from the FNM 10-K filed Feb 26, 2009.
Table 24: Delinquency Status of Loans Underlying Alt-A and Subprime Private-Label Securities
Other-than-temporary Impairment Assessment on Alt-A and Subprime Private-Label Securities
Our other-than-temporary impairment assessment as of December 31, 2008, which included an evaluation of the individual performance of the securities and the potential for continued adverse developments, indicated a continued increase in the level of uncertainty as to whether we would collect all principal and interest amounts due in accordance with the contractual terms. As a result, we determined that we did not have sufficient persuasive evidence to conclude that the impairment of certain available-for-sale securities was temporary. For these securities, we recognized other-than-temporary impairment totaling $4.6 billion in the fourth quarter of 2008, of which $3.4 billion related to Alt-A securities with an unpaid principal balance of $10.1 billion as of December 31, 2008, and $967 million related to subprime securities with an unpaid principal balance of $4.0 billion as of December 31, 2008. Table 25 presents the other-than-temporary impairment losses recorded on our investments in Alt-A and subprime private-label securities in 2008, including the fourth quarter of 2008, 2007 and the cumulative other-than-temporary impairment losses that we have recognized on these investments as of December 31, 2008.