Synthetic Difference in Differences
Methodology
2025-09-22 v4 Econometrics
Abstract
We present a new estimator for causal effects with panel data that builds on insights behind the widely used difference in differences and synthetic control methods. Relative to these methods we find, both theoretically and empirically, that this "synthetic difference in differences" estimator has desirable robustness properties, and that it performs well in settings where the conventional estimators are commonly used in practice. We study the asymptotic behavior of the estimator when the systematic part of the outcome model includes latent unit factors interacted with latent time factors, and we present conditions for consistency and asymptotic normality.
Cite
@article{arxiv.1812.09970,
title = {Synthetic Difference in Differences},
author = {Dmitry Arkhangelsky and Susan Athey and David A. Hirshberg and Guido W. Imbens and Stefan Wager},
journal= {arXiv preprint arXiv:1812.09970},
year = {2025}
}