Commercial banks increased their stake in the residential MBS market to a record $1.360 trillion as of the end of 2011, with a lot of the growth coming in Ginnie Mae MBS. Bank MBS holdings rose 2.4 percent from the third to the fourth quarter as seven of the 10 largest bank MBS investors reported significant increases. Compared to the end of 2010, bank MBS holdings were up 10.3 percent over a period in which the outstanding supply of single-family MBS continued to decline. Commercial banks held a record 20.9 percent of outstanding residential MBS at the end of last year, based...(Includes two data charts)