A continued decline in GSE refinance activity helped contribute to an overall dip in the volume of single-family mortgages securitized by Fannie Mae and Freddie Mac in November, according to a new Inside The GSEs analysis. Fannie and Freddie issued $58.7 billion in single-family mortgage-backed securities in November, a 13.4 percent decline from October and a 6.2 percent decrease for the first 11 months of 2013.