Mora, RicardoReggio Ojeda, Iliana Gabriela2022-05-202022-05-202019-05-28Mora, R., & Reggio, I. (2019). Alternative diff-in-diffs estimators with several pretreatment periods. Econometric Reviews, 38 (5), pp. 465-486.0747-4938https://hdl.handle.net/10016/34873This 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.eng© 2017 Taylor & Francis Group, LLCAtribución-NoComercial-SinDerivadas 3.0 EspañaCommon trendsDifference-in-differencesIdentificationTreatment effectresearch articleC21C52Economíahttps://doi.org/10.1080/07474938.2017.1348683open access4655486Econometric Reviews38AR/0000023681