At least four possible explanations have been put forth for why the net demand for long-term issues may have increased, lowering the term premium. First, longer-maturity obligations may be more attractive because of more stable inflation, better-anchored inflation expectations, and a reduction in economic volatility more generally. With the benefit of hindsight, we now recognize that an important change occurred in the U.S. economy (and, indeed, in other major industrial economies as well) sometime in the mid-1980s. Since that time, the volatilities of both real GDP growth and inflation have declined significantly, a phenomenon that economists have dubbed the "Great Moderation"...  In that regard, it is interesting to observe that long-term forward rates were also low in the 1950s and 1960s. With long-term inflation expectations apparently anchored at low levels and with the prospect of continued economic stability, market participants may believe that it is appropriate to price bonds for an environment like that which prevailed four or five decades ago.

Whether the dominant cause of the Great Moderation is structural change, improved monetary policy, or simply good luck is an important question about which no consensus has yet formed. I have argued today that improved monetary policy has likely made an important contribution not only to the reduced volatility of inflation (which is not particularly controversial) but to the reduced volatility of output as well. Moreover, because a change in the monetary policy regime has pervasive effects, I have suggested that some of the effects of improved monetary policies may have been misidentified as exogenous changes in economic structure or in the distribution of economic shocks.

Although the U.S. economy has largely escaped any deflation since World War II, there are some well-founded reasons to presume that deflation is more of a threat to economic growth than is inflation. For one, the lower bound on nominal interest rates at zero threatens ever-rising real rates if deflation intensifies. A related consequence is that even if debtors are able to refinance loans at zero nominal interest rates, they may still face high and rising real rates that cause their balance sheets to deteriorate.

Another concern about deflation resides in labor markets. Some studies have suggested that nominal wages do not easily adjust downward. If lower price inflation is accompanied by lower average wage inflation, then the prevalence of nominal wages being constrained from falling could increase as price inflation moves toward or below zero. In these circumstances, the effective clearing of labor markets would be inhibited, with the consequence being higher rates of unemployment.

Taken together, these considerations suggest that deflation could well be more damaging than inflation to economic growth. While this asymmetry should not be overlooked, several factors limit its significance. In particular, more rapid advances in productivity can make this asymmetry less severe. Fast growth of productivity, by buoying expectations of future advances of wages and earnings and thus aggregate demand, enables real interest rates to be higher than would otherwise be the case without restricting economic growth. Moreover, to the extent that more-rapid growth of productivity shows through to faster gains in nominal wages, there will be fewer instances in which nominal wages will be pressured to fall.

One also should not overstate the difficulties posed for monetary policy by the zero bound on interest rates and nominal wage inflexibility even in the absence of faster productivity growth. The expansion of the monetary base can proceed even if overnight rates are driven to their zero lower bound. The Federal Reserve has authority to purchase Treasury securities of any maturity and indeed already purchases such securities as part of its procedures to keep the overnight rate at its desired level. This authority could be used to lower interest rates at longer maturities. Such actions have precedent: Between 1942 and 1951, the Federal Reserve put a ceiling on longer-term Treasury yields at 2-1/2 percent. With respect to potential difficulties in labor markets, results from research remain ambiguous on the extent and persistence of downward rigidity in nominal compensation.

Clearly, it would be desirable to avoid deflation. But if deflation were to develop, options for an aggressive monetary policy response are available.