Inequality and unionization within the United States

Using data on U.S. state-level inequality from Frank, Sommeiller, Price, and Saez (2016) and state-level unionization data from Hirsch et al. (2001), this paper shows that unions have a negative impact on income inequality in U.S. states. In particular, higher rates of unionization decreased inequality, as measured by the Gini coefficient, the share of income accruing to the top 1% of earners, and the share of income accruing to the top 10% of earners. The findings are robust across several estimation methods and also when union coverage is used as an alternative to the percent of workers in unions.