Yiqing Xu
Generalized Synthetic Control Method: Causal Inference with Interactive Fixed Effects Models
University of California, San Diego
differenceindifferences commonly used causal inference timeseries crosssectional data requires assumption average outcomes treated control units would followed parallel paths absence treatment paper propose method relaxes oftenviolated assumption also unifies synthetic control method abadie diamond hainmueller 2010 linear fixed effects models simple framework special case imputes counterfactuals treated unit using control group information based linear interactive fixed effects model incorporates unitspecific intercepts interacted timevarying coefficients method several advantages first allows treatment correlated unobserved unit time heterogeneities reasonable modeling assumptions second generalizes synthetic control method case multiple treated units variable treatment periods improves efficiency interpretability third builtin crossvalidation procedure avoids specification searches thus easy implement empirical example election day registration voter turnout united states provided