Stevenson and Wolfers provide a number of possible reasons why this occurred, including non-comparable data over time, and increasing income inequality in the US during this period.

史蒂文森和沃尔弗斯给出了很多可能因素，解释造成此现象发生的原因，其中包括随着时间的消逝数据的不具可比性和这段时期内美国收入增加的日渐不平等。

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But which is the anomaly: the earlier period of high tax rates and rapidly growing state involvement in the economy, or the rising inequality of the past 30 years?

那么到底是什么不正常的：是早年的高税率和国家对经济迅速深化的介入，还是过去30年不平等的加剧？

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Surprisingly, over the same period global inequality has fallen, from 0.66 in the mid-1980s to 0.61 in the mid-2000s, according to Xavier Sala-i-Martin, an economist at Columbia University.

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The authors say it is no coincidence that inequality in hourly wages increased by over 40% during the same period.

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