The Effect of Large-Scale Anti-Contagion Policies on the Coronavirus (COVID-19) Pandemic

Solomon Hsiang; Daniel Allen; Sebastien Annan-Phan; Kendon Bell; Ian Bolliger; Trinetta Chong; Hannah Druckenmiller; Andrew Hultgren; Luna Yue Huang; Emma Krasovich; Peiley Lau; Jaecheol Lee; Esther Rolf; Jeanette Tseng; Tiffany Wu

Overall, our results indicate that large-scale anti-contagion policies are achieving their intended objective of slowing the growth rate of COVID-19 infections. Because infection rates in the countries we study would have initially followed rapid exponential growth had no policies been applied, our results suggest that these ongoing policies are currently providing large health benefits. For example, we estimate that there would be roughly 621× the current number of infections in South Korea, 36× in Italy, and 153× in Iran if large-scale policies had not been deployed during the early weeks of the pandemic. Consistent with process-based simulations of COVID-19 infections, 2, 4, 10-12, 14, 17, 29 our empirical analysis of existing policies indicates that seemingly small delays in policy deployment likely produce dramatically different health outcomes. While the quantity of currently available data poses challenges to our analysis, our aim is to use what limited data exist to estimate the first-order impacts of unprecedented policy actions in an ongoing global crisis. As more data become available, empirical research findings will become more precise and may capture more complex interactions. For example, this analysis does not account for potentially important interactions between populations in nearby localities, 7, 33 nor the structure of mobility networks. 3, 4, 10, 12, 17, 34 Nonetheless, we hope the results we are able to obtain at this early stage of the pandemic can support critical decision-making, both in the countries we study and in the other 150+ countries where COVID-19 infections have been reported.