Hysteresis and Instability in the Natural Rate of Unemployment
指出长期菲利普斯曲线不仅包含垂直形态，还有向上和向下倾斜的形态。通过弗里德曼和菲尔普斯两种模型，发现自然失业率受通胀率或其变化过程影响，且模型不稳定，意味着一旦偏离，垂直的长期菲利普斯曲线无法恢复。
In this paper, it is pointed out that the long-run Phillips curve genus contains upward and downward sloping species as well as the vertical species. Tw o models are used: in one the rate of inflation helps determine the natural rate of unemployment, as proposed by Milton Friedman; in the other the process of mo ving from one inflation rate to another helps shape thenatural rate, according to the hysteresis effect proposed by Edmond Phelps. In both cases the resulting models are unstable, implying that a vertical long-run Phillips curve will not b e regained if disturbed. Copyright 1987 by The editors of the Scandinavian Journal of Economics.