通货膨胀加速器（英）

The Inflation Accelerator

Introduction

Recent rises in inflation have sparked interest in understanding price dynamics. This paper aims to measure how the slope of the Phillips curve fluctuates in U.S. macroeconomic time series. A key determinant of the Phillips curve's slope is the fraction of price changes, which tends to increase during periods of high inflation.

Model Development

The authors propose a tractable sticky price model where the fraction of price changes evolves endogenously over time. Unlike the menu cost model, this model is highly tractable and reduces to a one-equation extension of the Calvo model. The additional equation determines the fraction of price changes, leading to a powerful "inflation accelerator" that significantly increases the slope of the Phillips curve during high inflation periods.

Key Findings

1. Slope of the Phillips Curve: The model predicts that the slope of the Phillips curve ranges from 0.02 in the 1990s to 0.12 in the 1970s and 1980s.
2. Inflation Accelerator: An increase in the fraction of price changes increases inflation, particularly at higher initial inflation rates. Conversely, higher inflation increases firms' incentives to adjust prices, further boosting the fraction of price changes. This feedback loop is termed the "inflation accelerator," which accounts for the steepening of the Phillips curve during high inflation.
3. Economic Implications: Reducing inflation is less costly when inflation is high compared to when it is low.

Model Structure

The model considers a New Keynesian economy with multi-product firms selling a continuum of goods and choosing the fraction of prices to change each period, subject to an adjustment cost. The model includes decreasing returns to scale, which dampens the slope of the Phillips curve. Monetary policy targets nominal spending, and shocks to the growth rate of nominal spending are the only sources of aggregate fluctuations.

Additional Insights

1. Impulse Responses: In environments with high inflation, the real effects of monetary shocks are smaller due to higher steady-state frequency of price changes and increased responsiveness of firms to underlying trend inflation.
2. Phillips Curve Dynamics: The slope of the Phillips curve is composed of two terms: one similar to the Calvo model and another capturing the inflation accelerator. The latter term significantly increases the slope during high inflation.

Conclusion

The paper provides a new framework for understanding the dynamics of inflation and the Phillips curve, emphasizing the role of the inflation accelerator in amplifying the relationship between inflation and the fraction of price changes. This framework suggests that reducing inflation is more cost-effective when inflation is high.