The employment effects of the minimum wage: A selection ratio approach to measuring treatment effects
提出一种利用多个不完美对照组来测量二元处理效应的方法，应用于最低工资研究，通过比较边界县与邻近县等来估计就业影响，并包含可检验的假设。
Summary I develop a method for measuring a binary treatment's effects when more than one control group is available but each control group is imperfect. To study effects of the minimum wage, for example, I compare border counties where the minimum wage increases to the set of neighboring counties, the set of neighbor‐of‐neighboring counties, and so forth. The key innovation is to model the ratio of the biases present in these comparisons. Crucially, the model contains a testable implication. The method can address spillovers and, in another application, is used to measure treatment effects away from the discontinuity in a regression discontinuity design.