Researchers estimated the effects of 1,700 local, regional and national policies on the growth rate of infections across localities within China, South Korea, Italy, Iran, France and the United States.

Subnational data was compiled on daily infection rates, changes in case definitions and the timing of policy deployments, including: (1) travel restrictions (2) social distancing through the cancellations of events and suspensions of educational, commercial and religious activities (3) quarantines and lockdowns (4) additional policies such as emergency declarations and expansions of paid sick leave, from the earliest available dates to 6 April 2020.

The daily growth rate of infections in each locality in response to the collection of ongoing policies applied to that locality on that day was examined.