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

The estimates above describe the superposition of all policies deployed in each country, i.e. they represent, for each country, the average effect of policies on infection growth rates that we would expect to observe, if all policies enacted anywhere in the country were implemented simultaneously in a region of the country. We also estimate the effects of individual types of policies or clusters of policies that are grouped based on their similarity in goal (e.g., closing libraries and closing 5 . museums are grouped) or timing (e.g., policies that are generally deployed simultaneously in a certain country). In many cases, our estimates for these effects are statistically noisier than the estimates for all policies combined (presented above) because we are estimating multiple effects simultaneously. Thus, we are less confident in individual estimates and in their relative rankings. Estimated effects differ between countries, and policies are neither identical nor perfectly comparable in their implementation across countries or, in many cases, across different localities within the same country. Nonetheless, overall we estimate that almost all policies likely contribute to slowing the growth rate of infections (Figure 2c ), except two policies (social distancing in France and Italy) where point estimates are slightly positive, small in magnitude, and not statistically different from zero.