Through a series of large-scale asset purchase programs (LSAPs), the Federal Reserve’s balance sheet expanded to include more longer-term Treasury securities and two additional asset classes, agency debt and agency mortgage-backed securities (MBS).1 Agency MBS currently represent more than 40 percent of the System Open Market Account (SOMA) domestic portfolio.2  Furthermore, in order to maintain the size of the SOMA’s agency holdings, the New York Fed’s Open Market Trading Desk (the Desk) continues to reinvest principal paydowns on agency MBS and agency debt into agency MBS each month.3 In my remarks today, I will share some reflections on LSAPs at the ZLB and the flexibility that access to the agency MBS market gives the Federal Reserve to execute such programs. Before I begin, however, let me remind you that the views I express are my own and do not necessarily reflect those of the Federal Reserve 1 / 10  BIS central bankers' speeches  Bank of New York or the Federal Reserve System. Large-Scale Asset Purchase Programs Currently, all the major advanced-economy central banks are either at or close to the zero lower bound.
In November 2008, there were significant dislocations in many financial markets, especially in the markets for the U.S. federal housing agencies’ securities. 23 In addition, the housing market was a focal point of the financial crisis. To help support the housing market and improve conditions in financial markets, the FOMC announced an LSAP program on November 25, 2008, that consisted of purchases of agency debt and agency MBS.24 The stated purpose of this program was to “reduce the cost and increase the availability of credit for the purchase of houses, which in turn should support housing markets and foster improved conditions in financial markets more generally. "25 Research suggests that this program reduced “abnormal pricing” in agency MBS— the component of the spread considered to be due to market dysfunction—by about 70 basis points over its first six months.26 In that same time period, the spread of agency MBS repurchase agreements (repos) to Treasury repos fell from more than 200 basis points to near zero. In the framework noted above, this LSAP worked primarily through the market functioning channel. However, research also suggests that borrowing costs were lowered more broadly 27 6 / 10  BIS central bankers' speeches  through a portfolio balance effect.27 Overall, the Desk’s purchases, aided by the lowering of fed funds to the ZLB in December 2008, resulted in lower mortgages rates, which in turn reduced the cost of home purchases and allowed existing borrowers to refinance at more attractive terms.