phillips curve_laffer curve_phillips curve公式(7)

The unemployment rate in the United States was 3。4 percent in 1968。 U。S。phillips curve unemployment peaked in the early 1980s at 10。8 percent and fell back substantially, so that by 2000 it again stood below 4 percent。

Modern macroeconomic models often employ another version of the Phillips curve in which the output gap replaces the unemployment rate as the measure of aggregate demand relative to aggregate supply. The output gap is the difference between the actual level of GDP and the potential (or sustainable) level of aggregate output expressed as a percentage of potential. This formulation explains why, at the end of the 1990s boom when unemployment rates were well below estimates of NAIRU, prices did not accelerate. The reasoning is as follows. Potential output depends not only on labor inputs, but also on plant and equipment and other capital inputs. At the end of the boom, after nearly a decade of rapid investment, firms found themselves with too much capital. The excess capacity raised potential output, widening the output gap and reducing the pressure on prices.

Many articles in the conservative business press criticize the Phillips curve because they believe it both implies that growth causes inflation and repudiates the theory that excess growth of money is inflation’s true cause. But it does no such thing. One can believe in the Phillips curve and still understand that increased growth, all other things equal, will reduce inflation. The misplaced criticism of the Phillips curve is ironic since Milton Friedman, one of the coinventors of its expectations-augmented version, is also the foremost defender of the view that “inflation is always, and everywhere, a monetary phenomenon.”

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