For a central bank to keep unemployment below the natural rate, it must keep outdoing itself, delivering inflation surprise after inflation surprise. 对于想把失业率维持在自然比率之下的央行来说，它必须保持不断地超越自身，传递出一个又一个的通胀惊奇。

　　Hence, Friedman reasoned, Keynesians were wrong to pin a low rate of unemployment to a given, high rate of inflation. 因而，弗里德曼分析道，凯恩斯主义把低失业率与给定的、高通胀率相挂钩是错误的。

　　To sustain unemployment even a little below the natural rate, inflation would need to accelerate year in, year out. 要想把失业率维持在哪怕是比自然比率低一点的地方，通胀也必需不断加速。

　　Friedman's and Phelps's natural rate became known as the “non-accelerating inflation rate of unemployment” (NAIRU). 弗里德曼和菲尔普斯的自然比率已成为众所周知的“非加速通胀型失业比率”(non-accelerating inflation rate of unemployment 简称NAIRU)。

　　No society could tolerate endlessly rising, or falling, inflation. 没有社会可能容忍上蹿下跳的通胀。

　　Phillips had observed a correlation in the data, but it was not one that policymakers could exploit in the long run. 菲利浦斯在数据中找到了一种关联，却不是决策者可以长期利用的那种。

　　“There is always a temporary trade-off between inflation and unemployment,” Friedman said. “There is no permanent trade-off.” “在通胀和失业之间，有的总是一种暂时的取舍，”弗里德曼说，“没有永久的取舍”。

　　Nearly 50 years on, that remains the premise on which rich-world central banks operate. 将近50年以后，这仍然是富裕世界的央行以之运作的前提。

　　When officials talk about the Phillips curve, they mean Friedman's temporary trade-off. 当官员们谈论菲利普斯曲线时，指的是弗里德曼的暂时取舍。

　　In the long run, they believe, unemployment will come to rest at the natural rate. 他们坚信，从长期来看，失业率终将止息于自然比率。

　　The idea has such influence partly because Friedman's and Phelps's contributions were so well timed. 这种思想之所以有如此的影响力，部分是因为弗里德曼和菲尔普斯的贡献正合时宜。

　　Before 1968, America had had two years with unemployment below 4% and inflation below 3%. 1968年之前，美国曾经有两年失业低于4%、通胀低于3%。

　　But when Friedman spoke, prices were indeed accelerating; inflation rose to 4.2% in 1968. 但是，弗里德曼讲话时，物价的确是在加速；1968年，通胀上涨到了4.2%。