HYSTERESIS IN A NEW KEYNESIAN MODEL
提出一种将滞后效应（持久失业具有结构性特征）纳入宏观经济模型的简单方法，通过失业持续时间增加导致劳动力市场匹配效率下降来建模，发现滞后效应会放大失业率和失业持续时间对生产率、偏好和货币冲击的反应，并提高自然失业率。
This paper provides a simple, tractable way of incorporating “hysteresis,” in which persistent unemployment takes on structural characteristics, into a macroeconomic model. Hysteresis is modeled as deterioration in labor market matching efficiency as the average duration of unemployment increases. This is embedded in a basic New Keynesian macro model. A decline in labor market matching efficiency would be consistent with the observed rightward shift of the Beveridge curve since the 2007–2009 recession. Hysteresis is shown to lead to larger and more persistent responses of the unemployment rate and unemployment duration to productivity, intertemporal preference, and monetary shocks. Hysteresis also generates an increase in the natural rate of unemployment.