Recent changes in the nature of the distribution dynamics of the US county incomes
研究了1970至2017年美国县级人均收入分布的演变，发现1990年代初以来不平等加剧且呈两极分化，教育和产业结构差异是主因，而政府医疗转移支付显著缓解了不平等。
Summary 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.