Nonbank lenders accounted for nearly half (48.7 percent) of the single-family mortgages securitized by Fannie Mae and Freddie Mac during the fourth quarter of 2015, according to a new Inside The GSEs analysis of mortgage-backed securities disclosures. The nonbank share of new GSE business has been on a steady march higher over the past few years as the top tier of depository institutions has repositioned their mortgage strategies and more lenders have participated directly in the securitization process. Back in 2013, nonbanks accounted for just 31.0 percent of new Fannie/Freddie business. The momentum did slow somewhat in 2015, however. After boosting their aggregate share by 12.9 percentage points to 43.9 percent in 2014, the nonbank...