These are mortgage loans that are "three monthly payments or more past due or in foreclosure".
The Fannie Mae serious delinquency rate peaked in February 2010 at 5.59%.
This matches last month as the lowest serious delinquency rate for Fannie Mae since June 2007.
By vintage, for loans made in 2004 or earlier (2% of portfolio), 2.50% are seriously delinquent. For loans made in 2005 through 2008 (4% of portfolio), 4.20% are seriously delinquent, For recent loans, originated in 2009 through 2018 (94% of portfolio), only 0.32% are seriously delinquent. So Fannie is still working through a few poor performing loans from the bubble years.
The increase in the delinquency rate in late 2017 was due to the hurricanes - there were no worries about the overall market.
I expect the serious delinquency rate will probably decline to 0.4 to 0.6 percent or so to a cycle bottom.
Note: Freddie Mac reported earlier.