Alternative diff-in-diffs estimators with several pretreatment periods |
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Authors: | Ricardo Mora Iliana Reggio |
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Affiliation: | Department of Economics, Universidad Carlos III, Getafe (Madrid), Spain |
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Abstract: | This paper deals with the identification of treatment effects using difference-in-differences estimators when several pretreatment periods are available. We define a family of identifying nonnested assumptions that lead to alternative difference-in-differences estimators. We show that the most usual difference-in-differences estimators imply equivalence conditions for the identifying nonnested assumptions. We further propose a model that can be used to test multiple equivalence conditions without imposing any of them. We conduct a Monte Carlo analysis and apply our approach to several recent papers to show its practical relevance. |
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Keywords: | Common trends difference-in-differences identification treatment effect |
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