How Different are Different Differences-in-Differences? A Large-Scale Meta-Analysis -- by Peter Hull

I thank Jason Abaluck, Zach Bleemer, Kirill Borusyak, Jiafeng Chen, Xavier Jaravel, Lihua Lei, Jonathan Roth, Pedro Sant’Anna, Jann Spiess, and Amanda Starc for helpful comments; Samuel Bazzi, Judson Boomhower, Enrico Cantoni, Pedro Dal Bó, Kyle Emerick, Luiz Felipe Fontes, Sebastian Galiani, Álvaro García-Marín, Matthew Gibson, Ricard Gil, Alex Hollingsworth, Aljoscha Janssen, Dean Karlan, Victor Lavy, Monica Martinez-Bravo, Benjamin Marx, Mathilde Muñoz, Peter Nencka, Mounu Prem, Paul Raschky, Jonah Rexer, and Edson Severnini for help replicating their papers; and OpenAI’s ChatGPT for excellent research assistance. Refine.ink was used to check for consistency and clarity. The views expressed herein are those of the author and do not necessarily reflect the views of the National Bureau of Economic Research.