Difference-in-Differences and Two-Way Fixed Effects Estimators: A Review of Some of the Recent Developments

Difference-in-Differences and Two-Way Fixed Effects Estimators are widely used to estimate policies’ effects: 26 of the 100 most cited papers published by the American Economic Review from 2015 to 2019 estimate such regressions. It has recently been shown that those estimators may be misleading, if the policy’s effect is heterogeneous between groups or over time. This course reviews a fast-growing literature that documents this issue, and that proposes alternative estimators robust to heterogeneous effects. Those robust estimators still rely on parallel trends assumptions, that may not hold exactly. This course also reviews a second strand of papers, that have proposed novel estimators when trends are not exactly parallel.

The lecturer Clément de Chaisemartin is Professor of Economics at Sciences Po since 2021. He is also a JPAL Affiliate. His research interests focus on econometric methods for policy evaluation, and on the economics of education. His work has been published in sever- al international journals, including the American Economic Review, Econometrica, the Review of Economic Studies, Quantitative Economics, the American Economic Journal: Applied Economics, and Clinical Infectious Diseases. In 2021, he was nominated for the best young French economist award. In 2019, his paper “Fuzzy Differences-in-Differences”, published in the Review of Economic Studies, received the AFSE-Malinvaud Prize.

The content is tailored towards PhD candidates and early career researchers. There is no participation fee, but space availability is limited. Priority will be given to researchers from UP and BSE.