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

Consistent with predictions from epidemiological models, 2, 18, 32 we find that the combined effect of all policies within each country reduces the growth rate of infections by a substantial and, except in the US, statistically significant amount ( Figure 2B ). For example, a locality in Italy with a baseline growth rate of 0.38 (national avg.) that deployed all policy actions used in Italy would be expected to lower its daily growth rate by 0.18 to 0.20. In general, the estimated total effects of policy packages are large enough that they can in principle offset a large fraction of, or even eliminate, the baseline growth rate of infections-although in several countries many localities are not currently deploying the full set of policies. Our estimate for the total growth effect of all US policies is quantitatively substantial (-0.25) but not statistically significant. US estimates are highly uncertain due to the short period of time for which data are available and because the time elapsed since these actions may be too short to observe a significant impact. In China, where policies have been enacted for over seven weeks, we observe that policy impacts have grown over time during the first three weeks of deployment (-0.11 to -0.33) . In all other countries except China, we only estimate an average effect for the entire interval of observation, due to the short temporal length of the sample.