COVID-19 Mobility Policies Impacts: How Credible are Difference-in-Differences Estimates?

63 Pages Posted: 12 Aug 2021

See all articles by Joakim Weill

Joakim Weill

Board of Governors of the Federal Reserve System

Mathieu Stigler

Stanford University, Center on Food Security and the Environment

Olivier Deschenes

University of California, Santa Barbara - College of Letters & Science - Department of Economics; National Bureau of Economic Research (NBER); IZA Institute of Labor Economics

Michael Springborn

University of California, Davis - College of Agricultural and Environmental Sciences - Department of Environmental Science and Policy

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Date Written: July 23, 2021

Abstract

The COVID-19 pandemic brought unprecedented policy responses and a large literature evaluating their impacts. This paper re-examines and add to the evidence on the impact of COVID-19 mobility-restricting policies on mobility indicators. We first find that two-way fixed effects estimates are not robust to minor specification changes, where the same policy can be found to significantly increase or decrease mobility, depending on the specification. Therefore, due to the large number of researcher’s degrees-of-flexibility, researchers can focus on a set of results that appears stable, while ignoring problematic ones. Further, recently developed heterogeneity-robust difference- in-differences methods only partially mitigate these issues.

Note: Funding: This research was supported by the University of California, Grant R00RG2419.

Declaration of Interests: None to declare

Keywords: COVID-19, social distancing, mobility, difference-in-differences, researcher degrees of flexibility

JEL Classification: I12, I18, C18, C23, H75

Suggested Citation

Weill, Joakim and Stigler, Matthieu and Deschenes, Olivier and Springborn, Michael, COVID-19 Mobility Policies Impacts: How Credible are Difference-in-Differences Estimates? (July 23, 2021). Available at SSRN: https://ssrn.com/abstract=3896512 or http://dx.doi.org/10.2139/ssrn.3896512

Joakim Weill (Contact Author)

Board of Governors of the Federal Reserve System ( email )

20th Street and Constitution Avenue NW
Washington, DC 20551
United States

Matthieu Stigler

Stanford University, Center on Food Security and the Environment ( email )

Stanford, CA 94305
United States

HOME PAGE: http://https://fse.fsi.stanford.edu/

Olivier Deschenes

University of California, Santa Barbara - College of Letters & Science - Department of Economics ( email )

UC Santa Barbara
Santa Barbara, CA 93106
United States

National Bureau of Economic Research (NBER) ( email )

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

IZA Institute of Labor Economics ( email )

P.O. Box 7240
Bonn, D-53072
Germany

Michael Springborn

University of California, Davis - College of Agricultural and Environmental Sciences - Department of Environmental Science and Policy ( email )

HOME PAGE: http://https://springborn.faculty.ucdavis.edu/

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