Tracking Public and Private Responses to the COVID-19 Epidemic

This paper examines the determinants of social distancing during the shutdown phase of the COVID-19 epidemic. We classify state and local government actions, and we study multiple proxies for social distancing based on data from smart devices. Mobility fell substantially in all states, even ones that did not adopt major distancing mandates. Most of the fall in mobility occurred prior to the most stringent sanctions against movement, such as stay-at-home laws. However, we find evidence suggesting that state and local policies did have an independent effect on mobility even after the large initial reductions occurred. Event studies show that early and information-focused actions such as first case announcements, emergency declarations, and school closures reduced mobility by 1–5 percent after five days. Between March 1 and April 14, average time spent at home grew from 9.1 hours to 13.9 hours. We find, for example, that without state emergency declarations, hours at home would have been 11.3 hours in April, suggesting that 55 percent of the growth is associated with policy and 45 percent is associated with (non-policy) trends. State and local government actions induced changes in mobility on top of a large and private response across all states to the prevailing knowledge of public health risks.