The surge in refinancings this fall pushed Fannie Mae's issuance of MBS to $63.7 billion in November, up 20% from the prior month.

The secondary market agency also reported Friday morning that its commitments to purchase loans from lenders jumped 12% from October to $61.3 billion in November.

During the previous refinancing boom that peaked in the last two months of 2010 — Fannie loan commitments crested at $62 billion in December. In December 2010, Fannie also issued $83.7 billion in MBS.

November's activity report shows Fannie executives don't have to worry about breaching the conservatorship agreement when it comes to reducing its giant mortgage investment portfolio to $729 billion by Dec. 31.

The GSE has shrunk the portfolio of mortgage loans and MBS by 10% over the past 12 months to $713.5 billion as of Nov. 30.

Meanwhile, Fannie's single-family delinquency rate was unchanged in November. The percentage of guaranteed loans 90 days or more past due has been stuck at 4% for three months.

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