Fannie Mae last month reclaimed some of the market share Freddie Mac snagged in October and November as GSE single-family business volume skidded toward yearend. Fannie issued $43.99 billion of single-family mortgage-backed securities in December, a tidy 4.9 percent increase from the previous month. Freddie’s $30.03 billion in production tumbled 19.2 percent from November. That gave Fannie a 59.4 percent share of the GSE market in December, in line with historical trends. Freddie posted big increases in volume during October and November, pushing its GSE market share to 46.4 percent for the two-month period. Even with the return to more normal...