New business activity at Fannie Mae and Freddie Mac fell sharply in the fourth quarter of 2014, but the top tier of mortgage sellers took more than their share of the decline, according to a new Inside Mortgage Trends analysis of mortgage-backed securities data. Total single-family MBS production by the two government-sponsored enterprises declined by 36.1 percent from the third quarter to the fourth quarter of 2013. But the top five GSE sellers posted a combined 45.9 percent ... [Includes two data charts]