Alternative diff-in-diffs estimators with several pretreatment periods. (28th May 2019)

• Record Type: Journal Article
• Authors: Mora, Ricardo; Reggio, Iliana
• Is Part Of: Econometric reviews. Volume 38:Number 5(2019)
• Page Start: 465
• Page End: 486
• Publication Date: 2019-05-28
• Subjects: Common trends -- difference-in-differences -- identification -- treatment effect; C21 -- C52; Econometrics -- Periodicals; 330.015195
• DOI: 10.1080/07474938.2017.1348683
• Languages: English
• ISSNs: 0747-4938

Abstract

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.