In 2002, before he was named Federal Reserve Chairman, Ben Bernanke gave an interesting talk on the dangers of deflation:

With inflation rates now quite low in the United States, however, some have expressed concern that we may soon face a new problem--the danger of deflation, or falling prices. That this concern is not purely hypothetical is brought home to us whenever we read newspaper reports about Japan, where what seems to be a relatively moderate deflation--a decline in consumer prices of about 1 percent per year--has been associated with years of painfully slow growth, rising joblessness, and apparently intractable financial problems in the banking and corporate sectors.

To be clear, Bernanke is not talking about a simple drop in investment assets, but a general deflation in consumer prices as well.

Bernanke then outlined how the Fed can avoid deflation:

[T]here are several measures that the Fed (or any central bank) can take to reduce the risk of falling into deflation.

First, the Fed should try to preserve a buffer zone for the inflation rate, that is, during normal times it should not try to push inflation down all the way to zero. Most central banks seem to understand the need for a buffer zone. For example, central banks with explicit inflation targets almost invariably set their target for inflation above zero, generally between 1 and 3 percent per year. Maintaining an inflation buffer zone reduces the risk that a large, unanticipated drop in aggregate demand will drive the economy far enough into deflationary territory to lower the nominal interest rate to zero. Of course, this benefit of having a buffer zone for inflation must be weighed against the costs associated with allowing a higher inflation rate in normal times.

Second, the Fed should take most seriously--as of course it does--its responsibility to ensure financial stability in the economy. Irving Fisher (1933) was perhaps the first economist to emphasize the potential connections between violent financial crises, which lead to "fire sales" of assets and falling asset prices, with general declines in aggregate demand and the price level. A healthy, well capitalized banking system and smoothly functioning capital markets are an important line of defense against deflationary shocks. The Fed should and does use its regulatory and supervisory powers to ensure that the financial system will remain resilient if financial conditions change rapidly. And at times of extreme threat to financial stability, the Federal Reserve stands ready to use the discount window and other tools to protect the financial system, as it did during the 1987 stock market crash and the September 11, 2001, terrorist attacks.

Third, as suggested by a number of studies, when inflation is already low and the fundamentals of the economy suddenly deteriorate, the central bank should act more preemptively and more aggressively than usual in cutting rates . . . . By moving decisively and early, the Fed may be able to prevent the economy from slipping into deflation, with the special problems that entails.

As I have indicated, I believe that the combination of strong economic fundamentals and policymakers that are attentive to downside as well as upside risks to inflation make significant deflation in the United States in the foreseeable future quite unlikely.

Bernanke's 2002 analysis appears to be very sound.