However, more recently, as the pace of economic growth has slowed somewhat, longer-term interest rates have fallen and mortgage refinancing activity has picked up. Increased refinancing has in turn led the Fed’s holding of agency MBS to run off more quickly than previously anticipated. Although mortgage prepayment rates are difficult to predict, under the assumption that mortgage rates remain near current levels, we estimated that an additional $400 billion or so of MBS and agency debt currently in the Fed’s portfolio could be repaid by the end of 2011. .
