The employment effects of the minimum wage: A selection ratio approach to measuring treatment effects

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.