Wage inequality and urban density
利用1970-1990年美国大都市区数据，发现人口密度与三种工资不平等指标（无条件百分位差距、残差百分位差距、教育组间差距）之间存在显著且稳健的负相关关系。
While a sizable body of research has studied the relationship between aggregate productivity and geographic density, little work has considered how density influences the distribution of productivity across workers. This paper offers some descriptive evidence on the relationship between three measures of earnings inequality—unconditional percentile gaps, residual percentile gaps, between education-group gaps—and population density across a sample of US metropolitan areas between 1970 and 1990. On the whole, the findings reveal a significant and strikingly robust negative association between density and each measure.