There is a limit to how much monetary policy can do to help the economy during a period of severe economic decline, such as the United States encountered during the 1930s. The monetary policy remedy to economic decline is to increase the amount of money in circulation, thereby cutting interest rates. But once interest rates reach zero, the Fed can do no more.

The United States has not encountered this situation, which economists call the "liquidity trap," in recent years, but Japan did during the late 1990s. With its economy stagnant and interest rates near zero, many economists argued that the Japanese government had to resort to more aggressive fiscal policy, if necessary running up a sizable government deficit to spur renewed spending and economic growth.