After mortgage giant Freddie Mac ($0.00 0%) reported a 13% drop in mortgage purchases in November, Fannie Mae ($0.00 0%) shows its book of business declined at an annualized rate of 6.7% in the same month, according to its monthly summary.

The performance of Fannie’s mortgages continue to deteriorate. The single-family serious delinquency rate climbed another 26 basis points (bps) to 4.98% in October, which is the most recent month of data. The multifamily delinquency rate dipped to 0.61% in October from 0.62% in the previous month.

The delinquency rate in both categories swelled from October 2008, when the single-family delinquency rate was 1.89% and 0.21% for multifamily loans.

Fannie reported $2.81bn in total mortgage-backed securities (MBS) and other guarantees at the end of November. The government-sponsored enterprise (GSE) issued $40.3m of MBS in November, a 2.7% drop from October. It’s total amount of issuance reached $752.4m in 2009 with one month to go.

Fannie’s gross mortgage portfolio declined at an annualized rate of 26.1% to $752.2m in November.

Write to Jon Prior.