Sequential Synthetic Difference in Differences

Fuente: arXiv
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Main Authors: Arkhangelsky, Dmitry, Samkov, Aleksei
Format: Preprint
Published: 2024
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author Arkhangelsky, Dmitry
Samkov, Aleksei
author_facet Arkhangelsky, Dmitry
Samkov, Aleksei
contents We propose the Sequential Synthetic Difference-in-Differences (Sequential SDiD) estimator for event studies with staggered treatment adoption, particularly when the parallel trends assumption fails. The method uses an iterative imputation procedure on aggregated data, where estimates for early-adopting cohorts are used to construct counterfactuals for later ones. We prove the estimator is asymptotically equivalent to an infeasible oracle OLS estimator within a linear model with interactive fixed effects. This key theoretical result provides a foundation for standard inference by establishing asymptotic normality and clarifying the estimator's efficiency. By offering a robust and transparent method with formal statistical guarantees, Sequential SDiD is a powerful alternative to conventional difference-in-differences strategies.
format Preprint
id arxiv_https___arxiv_org_abs_2404_00164
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Sequential Synthetic Difference in Differences
Arkhangelsky, Dmitry
Samkov, Aleksei
Econometrics
We propose the Sequential Synthetic Difference-in-Differences (Sequential SDiD) estimator for event studies with staggered treatment adoption, particularly when the parallel trends assumption fails. The method uses an iterative imputation procedure on aggregated data, where estimates for early-adopting cohorts are used to construct counterfactuals for later ones. We prove the estimator is asymptotically equivalent to an infeasible oracle OLS estimator within a linear model with interactive fixed effects. This key theoretical result provides a foundation for standard inference by establishing asymptotic normality and clarifying the estimator's efficiency. By offering a robust and transparent method with formal statistical guarantees, Sequential SDiD is a powerful alternative to conventional difference-in-differences strategies.
title Sequential Synthetic Difference in Differences
topic Econometrics
url https://arxiv.org/abs/2404.00164