A day after mortgage giant Freddie Mac (FRE) said its purchases and issuances were down in October, sister government-sponsored enterprise (GSE) Fannie Mae (FNM) revealed its book of business declined at an annualized rate of 3.1% in the same month. Fannie's mortgage-backed securities (MBS) and other guarantees totaled $2.82bn at the end of the month. The GSE issued $40.74m of MBS in October -- down 31% from $59.25m in September -- bringing total issuance in 2009 up to $712.1m. Fannie's gross mortgage portfolio declined at an annualized rate of 27.8% and stood at $771.4m at the end of the month, according to the monthly summary (available to download here). The performance of Fannie's mortgages continued to decline in the previous month. The single-family serious delinquency rate rose 27 bps to 4.72% in September -- the most recent month of data. The multi-family serious delinquency rate rose 6 bps to 0.62%. These rates are up from 1.72% and 0.16% respectively in September 2008, according to Fannie's data. Write to Diana Golobay.