We study the evolution of the cross-sectional distributions of county-level per capita income in the United States from 1970 to 2017. We confirm previous findings of convergence in pre-transfer income during the 1970s and 1980s but present new evidence of rising inequality since the early 1990s, which is characterized by bipolarization. Cross-county differences in education and industry composition explain much of this recent trend, which almost disappears in post-transfer incomes. Among the various government transfer programs, medical benefits play the greatest role in making the distribution less unequal.

中文翻译：

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美国各县收入分配动态性质的近期变化

我们研究了 1970 年至 2017 年美国县级人均收入横截面分布的演变。我们证实了先前关于 1970 年代和 1980 年代转移前收入趋同的发现，但提出了自 2017 年以来不平等加剧的新证据。 20世纪90年代初，其特点是两极分化。教育和行业构成方面的跨县差异在很大程度上解释了最近的这一趋势，这种趋势在转移后收入中几乎消失了。在各种政府转移支付项目中，医疗福利对减少分配不平等的作用最大。