Fannie Mae and Freddie Mac dominated the residential mortgage market in 2013, albeit to a lesser degree, than the GSEs had during the previous 12-month period, according to a new Inside The GSEs analysis. Fannie and Freddie issued a combined $1.571 trillion of single-family mortgage-backed securities in 2013, which equaled 73.8 percent of total market production. That was down from 75.7 percent in 2012.