To combat the Great Recession and its long-lingering aftermath, leading central banks have pulled some $10 trillion out of thin air. Governments of the world's principal economies have rung up almost $20 trillion in deficit spending. We often hear that the authorities have done too little. Perhaps they have done too much.

Not so long ago, the authorities did hardly anything. In response to the severe, little-known economic slump of the early 1920s, they virtually sat on their hands. It is an often forgotten episode that suggests the potential for constructive federal inaction—and underscores the healing power of Adam Smith 's invisible hand.

Beginning in January 1920, something much worse than a recession blighted the world. The U.S. suffered the steepest plunge in wholesale prices in its history (not even eclipsed by the Great Depression), as well as a 31.6% drop in industrial production and a 46.6% fall in the Dow Jones Industrial Average. Unemployment spiked, and corporate profits plunged.