Despite lower mortgage rates, MBS prepayment speeds slowed across the board in December, particularly for the recent low coupons, while speeds for higher coupons were up slightly, according to securitization analysts. Researchers varied slightly in their estimates, saying speeds for 30-year Fannie Mae securities slowed 2-6 conditional prepayment rate for the recent low coupons (3.5-4.5 percent from 2011 and 2010). Barclays Capital analysts attributed the slowdown to reduced refinancing activity during the December holiday season. The weighted average CPR for all Fannie Mae MBS declined to...