Income inequality has been lower in periods when trade unionism has been strong. Using observations on wages by occupation, by geography, and by gender in collective bargaining contracts from the 1940s to the 1970s, patterns in movements of wage differentials are revealed. As wages increased, some contracts maintained relative wage differentials constant, some maintained absolute differences in wages constant, others combined these two patterns, and some did not reveal an obvious pattern. The patterns persisted even as price inflation increased in the 1970s. The dominant pattern implies a reduction in inequality as usually measured.

中文翻译：

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二十世纪中叶美国劳动力市场中的工资差异，讨价还价协议和工会主义

在工会主义强烈的时期，收入不平等程度降低了。使用从1940年代到1970年代的集体谈判合同中按职业，地理和性别划分的工资观察结果，揭示了工资差异的变化方式。随着工资的增加，一些合同使相对工资差异保持恒定，一些合同使工资的绝对差异保持恒定，另一些合同则将这两种模式结合在一起，而有些则没有显示出明显的模式。即使在1970年代价格上涨加剧的情况下，这种模式依然存在。占主导地位的模式意味着通常所衡量的不平等程度的降低。