Download This PaperThe Triple Difference Estimator
26 Pages Posted: 23 Apr 2020
Date Written: April 22, 2020
Abstract
Triple difference has become a widely used estimator in empirical work. A close reading of articles in top economics journals reveals that the use of the estimator to a large extent rests on intuition. The identifying assumptions are neither formally derived nor generally agreed on. We give a complete presentation of the triple difference estimator, and show that even though the estimator can be computed as the difference between two difference-in-differences estimators, it does not require two parallel trend assumptions to have a causal interpretation. The reason is that the difference between two biased difference-in-differences estimators will be unbiased as long as the bias is the same in both estimators. This requires only one parallel trend assumption to hold.
Keywords: Triple difference, difference-in-difference-in-differences, difference-in-differences, DID, DiDiD, parallel trend assumption
JEL Classification: C10, C18, C21
Suggested Citation: Suggested Citation
Andreas Olden (Contact Author)
NHH Norwegian School of Economics - Department of Business and Management Science ( email )
Helleveien 30
Bergen, NO-5045
Norway
Jarle Moen
Norwegian School of Economics (NHH) - Department of Business and Management Science ( email )
Helleveien 30
Bergen, NO-5045
Norway