Fannie Mae’s (FNM) book of business grew at an annualized rate of 3.7% in August to $3.2trn at the end of the month, according to the mortgage giant’s monthly summary. While Fannie’s issuances fell for the second straight month and the delinquency rate continued its climb, its total mortgage portfolio stayed at July’s level. Fannie purchases and securitizes mortgage loans and for August, posted $62.1bn of issuance, down 22% from $79.7bn in July but almost double the $32bn in August 2008. The gross mortgage portfolio for August held at July’s level of $779.4bn at the end of the month, but it is an increase from $759.9bn in August of last year. The rate of conventional single-family mortgages serious delinquent rose 19bps to 2.66% in July, compared to 0.80% in July 2008. The rate of serious delinquencies among multifamily mortgages jumped to 0.56% in July from 0.51% in June, compared to 0.13% from July of last year. Write to Jon Prior.