The mix of single-family mortgages securitized by Fannie Mae and Freddie Mac during the third quarter of 2013 continued to shift toward purchase mortgages, according to a new Inside Mortgage Trends analysis of the government-sponsored enterprise market. Purchase mortgages accounted for 36.7 percent of Fannie/Freddie business during the third quarter, up from 23.9 percent during the previous period. It was the highest purchase-mortgage share of GSE business since the market collapse ... [Includes two data charts]