Fannie Mae and Freddie Mac saw declines in the flow of purchase and refinance loans into single-family mortgage-backed securities last month, starting 2018 on a sour note. The two GSEs produced a total of $67.48 billion of new single-family MBS in January, according to a new Inside The GSEs analysis and ranking. That was down 8.8 percent from the previous month and off 26.4 percent from January 2017. It was the GSEs’ weakest monthly output since May 2017, and it would have been worse had Fannie not come up with $4.69 billion in mortgage securities backed by modified loans. Including those mod-backed deals, Fannie issuance was up 5.0 percent from December. Without them, the company’s new MBS issuance fell 5.7 percent in January.