by Calculated Risk on 3/08/2010 05:01:00 PM

From Brian Sack, Executive Vice President, Federal Reserve Bank of New York: Preparing for a Smooth (Eventual) Exit. Excerpts on MBS:

The Federal Reserve is approaching the scheduled end of its large-scale asset purchases. We have bought $169 billion of agency debt to date, nearly fulfilling our plan to purchase "about $175 billion." For MBS, we have only about $30 billion of purchases remaining to reach our $1.25 trillion target. In addition, we completed $300 billion of purchases of Treasury securities late last year. Looking across these programs, we have now purchased $1.69 trillion of assets, bringing us 98 percent of the way through our scheduled purchases.

My view is that the purchase programs have helped to hold down longer-term interest rates, thereby supporting economic activity. With the conclusion of the programs approaching, the Desk has been tapering the pace of its purchases of agency debt and MBS. However, even as the pace of our purchases has slowed, longer-term interest rates have remained low, and MBS spreads over Treasury yields have remained tight. This pattern suggests that the effects of the purchases have been primarily associated with the stock of the Fed's holdings rather than with the flow of its purchases. In that case, the market effects of the purchase program will only slowly unwind as the balance sheet shrinks gradually over time.
...
Chairman Bernanke noted that the Fed's holdings of agency debt and MBS are being allowed to roll off the balance sheet, without reinvestment, as those securities mature or are prepaid, and that the FOMC may choose to redeem some of its holdings of Treasury securities in the future, as well.

With this approach, the FOMC would be shrinking its balance sheet in a gradual and passive manner. That, in my view, is a crucial message for the markets. It should limit any reversal of the portfolio balance effects described earlier, effectively putting reductions in asset holdings in the background for now as a policy instrument. As long as this approach is maintained, it would leave the adjustment of short-term interest rates as the more active policy instrument—the one that would carry the bulk of the work in tightening financial conditions when appropriate.

This approach is cautious in several dimensions. First, a decision to shrink the balance sheet more aggressively could be disruptive to market functioning. Second, a more aggressive approach would risk an immediate and substantial rise in longer-term yields that, at this time, would be counterproductive for achieving the FOMC's objectives. Third, the effects of swings in the balance sheet on the economy are difficult to calibrate and subject to considerable uncertainty, given our limited history with this policy tool. And fourth, policymakers do not need to use this tool to tighten financial conditions. They can tighten financial conditions as much as needed by raising short-term interest rates, offsetting any lingering portfolio balance effects arising from the still-elevated portfolio.

Even under this cautious strategy of relying only on redemptions, the Federal Reserve could achieve a considerable decline in the size of its balance sheet over time. From now to the end of 2011, we project that more than $200 billion of the agency debt and MBS held by the Federal Reserve will mature or be prepaid, though the actual total will depend on the path of long-term interest rates and the prepayment behavior of mortgage holders. Thus, the Fed's asset holdings would shrink meaningfully if the FOMC maintains its current strategy of not reinvesting those proceeds. In addition, about $140 billion of Treasury securities mature between now and the end of 2011, giving the FOMC scope to reduce its asset holdings even further if it chooses to not replace some of those maturing securities.

While the passive strategy of relying on redemptions may be appropriate for now, it might not be sufficient over the longer-term. One problem is that relying only on redemptions would still leave some MBS holdings on our balance sheet for several decades. As indicated in the minutes from the January meeting, the FOMC intends to return to a Treasuries-only portfolio over time. This consideration could motivate the FOMC to sell its agency debt and mortgage-backed securities at some point, once the economic recovery has progressed sufficiently.
emphasis added

I recommend reading the entire speech, especially the section titled: Market Conditions: At Risk on Exit?

Sack believes there will be little increase in the spread between mortgage rates and the Ten Year Treasury yield when the MBS purchase program ends. Right now the Fed plans on letting the MBS roll off the balance sheet, so in Sack's view the impact on rates should be gradual.