In the June addendum, the FOMC noted that reducing the Fed’s securities holdings will result in a declining supply of reserve balances, and that it anticipates reducing the quantity of reserve balances to a level “appreciably below that seen in recent years but larger than before the financial crisis.” New York Fed staff projections for possible paths of the Fed’s securities portfolio—constructed using a distribution of market participants’ surveyed expectations for the future size of the Fed’s balance sheet (conditional on not moving to the zero lower bound at any point between now and 2025), along with some staff modeling to fill in details—suggest it will take at least several years for the balance sheet to reach its “normal” size.14 Uncertainty about the time of normalization arises from numerous sources, including future levels and variability of demand for different types of Fed liabilities, the pace at which the agency MBS portfolio will pay down, and of course the economic outlook. Assuming that balance sheet normalization continues uninterrupted, it seems likely that the future balance sheet size will be driven largely by changes in longer-run demand for Fed liabilities —in contrast to the asset-driven balance sheet of the past decade. The FOMC explains in the June addendum that reserve balances will be driven by the banking system’s demand for reserves and the Committee’s decisions about how to implement monetary policy in the future.
Then, in September 2011, the FOMC announced that repayments from these securities would instead be reinvested in agency MBS to help support conditions in mortgage markets.29 The FOMC then maintained reinvestments, including Treasury rollovers, until commencing balance sheet normalization last month.30 Keeping the Fed’s holdings of longer-term securities at sizable levels helped to maintain accommodative financial conditions as economic conditions strengthened. This is because, in addition to the acquisition of securities through asset purchases, the period over which the central bank intends to hold its securities helps to shape market participants’ expectations about the size and duration of assets available to the public. Extending the holding period through reinvestments prolongs this so-called stock effect. The 2010 episode when the Fed was not reinvesting agency-related principal payments demonstrated both term premium effects that might have been expected to be associated with a reduction in the Fed’s securities holdings and the risks associated with an unexpected increase in the publicly-held stock of agency MBS. As we normalize the size of the balance sheet, maintaining redemption caps throughout the process (and continuing to reinvest any principal payments received in excess of those caps) provides an insurance mechanism that limits the amount of variation in the pace at which securities, particularly mortgages, will flow back into private hands. Lesson 5: Credible communications influence the effectiveness of asset purchase programs As a general matter, monetary policy transmits more smoothly when market participants are able to understand and anticipate central bank actions.