COVID-19 Time-varying Reproduction Numbers Worldwide: An Empirical Analysis of Mandatory and Voluntary Social Distancing

58 Pages Posted: 17 Apr 2020 Last revised: 24 Mar 2021

See all articles by Alexander Chudik

Alexander Chudik

Federal Reserve Banks - Federal Reserve Bank of Dallas

M. Hashem Pesaran

University of Southern California - Department of Economics

Alessandro Rebucci

Johns Hopkins University - Carey Business School; National Bureau of Economic Research (NBER); Centre for Economic Policy Research (CEPR)

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Date Written: March 15, 2021

Abstract

This paper estimates time-varying COVID-19 reproduction numbers worldwide solely based on the number of reported infected cases, allowing for under-reporting. Estimation is based on a moment condition that can be derived from an agent-based stochastic network model of COVID-19 transmission. The outcomes in terms of the reproduction number and the trajectory of per-capita cases through the end of 2020 are very diverse. The reproduction number depends on the transmission rate and the proportion of susceptible population, or the herd immunity effect. Changes in the transmission rate depend on changes in the behavior of the virus, reflecting mutations and vaccinations, and changes in people's behavior, reflecting voluntary or government mandated isolation. Over our sample period, neither mutation nor vaccination are major factors, so one can attribute variation in the transmission rate to variations in behavior. Evidence based on panel data models explaining transmission rates for nine European countries indicates that the diversity of outcomes results from the non-linear interaction of mandatory containment measures, voluntary precautionary isolation, and the economic incentives that governments provided to support isolation. These effects are precisely estimated and robust to various assumptions. As a result, countries with seemingly different social distancing policies achieved quite similar outcomes in terms of the reproduction number. These results imply that ignoring the voluntary component of social distancing could introduce an upward bias in the estimates of the effects of lock-downs and support policies on the transmission rates. The full set of estimation results and the replication package are available on the authors' websites.

Note: Funding: None to declare

Declaration of Interest: None to declare.

Keywords: COVID-19, SIR model, epidemics, multiplication factor, under-reporting, voluntary social distancing

JEL Classification: D0, F60, C4, I120, E7

Suggested Citation

Chudik, Alexander and Pesaran, M. Hashem and Rebucci, Alessandro, COVID-19 Time-varying Reproduction Numbers Worldwide: An Empirical Analysis of Mandatory and Voluntary Social Distancing (March 15, 2021). Johns Hopkins Carey Business School Research Paper No. 20-03, Available at SSRN: https://ssrn.com/abstract=3576703 or http://dx.doi.org/10.2139/ssrn.3576703

Alexander Chudik

Federal Reserve Banks - Federal Reserve Bank of Dallas ( email )

2200 North Pearl Street
PO Box 655906
Dallas, TX 75265-5906
United States

M. Hashem Pesaran

University of Southern California - Department of Economics ( email )

3620 South Vermont Ave. Kaprielian (KAP) Hall 300
Los Angeles, CA 90089
United States

Alessandro Rebucci (Contact Author)

Johns Hopkins University - Carey Business School ( email )

100 International Drive
Baltimore, MD 21202
United States

HOME PAGE: http://carey.jhu.edu/faculty-research/faculty-directory/alessandro-rebucci-phd

National Bureau of Economic Research (NBER) ( email )

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

Centre for Economic Policy Research (CEPR) ( email )

London
United Kingdom

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