  We study the estimation of heterogeneous effects of group-level policies,
using quantile regression with interactive fixed effects. Our approach can
identify distributional policy effects, particularly effects on inequality,
under a type of difference-in-differences assumption. We provide asymptotic
properties of our estimators and an inferential method. We apply the model to
evaluate the effect of the minimum wage policy on earnings between 1967 and
1980 in the United States. Our results suggest that the minimum wage policy has
a significant negative impact on the between-inequality but little effect on
the within-inequality.
