Lucas Critique - Examples

Examples

One important application of the critique (independent of proposed microfoundations) is its implication that the historical negative correlation between inflation and unemployment, known as the Phillips Curve, could break down if the monetary authorities attempted to exploit it. Permanently raising inflation in hopes that this would permanently lower unemployment would eventually cause firms' inflation forecasts to rise, altering their employment decisions. Said another way, just because high inflation was associated with low unemployment under early-twentieth-century monetary policy does not mean we should expect high inflation to lead to low unemployment under all alternative monetary policy regimes.

For an especially simple example, note that Fort Knox has never been robbed. However, this does not mean the guards can safely be eliminated, since the incentive not to rob Fort Knox depends on the presence of the guards. In other words, with the heavy security that exists at the fort today, criminals are unlikely to attempt a robbery because they know they are unlikely to succeed. But a change in security policy, such as eliminating the guards for example, would lead criminals to reappraise the costs and benefits of robbing the fort. So just because there are no robberies under the current policy does not mean this should be expected to continue under all possible policies.