The retained mortgage portfolios of Fannie Mae and Freddie Mac continued to decline through natural attrition during the first quarter of 2013, falling by 4.9 percent from the previous quarter, according to an Inside MBS & ABS analysis of earnings reports released by the two government-sponsored enterprises this week. Fannie and Freddie held $1.13 trillion in mortgage assets as of the end of March. With heavy refinance activity, the rate of decline in early 2013 was faster than it had been; GSE holdings were down 13.6 percent from year-ago levels. There was...[Included one data chart]