Difference-in-Differences Estimators When No Unit Remains Untreated

Fuente: arXiv
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Autori principali: de Chaisemartin, Clément, Ciccia, Diego, D'Haultfœuille, Xavier, Knau, Felix
Natura: Preprint
Pubblicazione: 2024
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author de Chaisemartin, Clément
Ciccia, Diego
D'Haultfœuille, Xavier
Knau, Felix
author_facet de Chaisemartin, Clément
Ciccia, Diego
D'Haultfœuille, Xavier
Knau, Felix
contents We consider treatment-effect estimation with a two-periods panel, where units are untreated at period one, and receive strictly positive doses at period two. First, we consider designs with some quasi-untreated units, with a period-two dose local to zero. We show that under a parallel-trends assumption, a weighted average of slopes of units' potential outcomes is identified by a difference-in-difference estimand using quasi-untreated units as the control group. We leverage results from the regression-discontinuity-design literature to propose a nonparametric estimator. Then, we propose estimators for designs without quasi-untreated units. Finally, we propose a test of the homogeneous-effect assumption underlying two-way-fixed-effects regressions.
format Preprint
id arxiv_https___arxiv_org_abs_2405_04465
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Difference-in-Differences Estimators When No Unit Remains Untreated
de Chaisemartin, Clément
Ciccia, Diego
D'Haultfœuille, Xavier
Knau, Felix
Econometrics
We consider treatment-effect estimation with a two-periods panel, where units are untreated at period one, and receive strictly positive doses at period two. First, we consider designs with some quasi-untreated units, with a period-two dose local to zero. We show that under a parallel-trends assumption, a weighted average of slopes of units' potential outcomes is identified by a difference-in-difference estimand using quasi-untreated units as the control group. We leverage results from the regression-discontinuity-design literature to propose a nonparametric estimator. Then, we propose estimators for designs without quasi-untreated units. Finally, we propose a test of the homogeneous-effect assumption underlying two-way-fixed-effects regressions.
title Difference-in-Differences Estimators When No Unit Remains Untreated
topic Econometrics
url https://arxiv.org/abs/2405.04465