Mobility Reduction and Covid-19 Transmission Rates

Bergman, N. K.; Fishman, R.

Assessing the contribution of mobility restrictions to the control of Covid-19 diffusion is an urgent challenge of global import. We analyze the relation between transmission rates (estimated effective reproduction numbers) and societal mobility levels using fine-grained daily mobility data from Google and Apple in an international panel of 87 countries and a panel of all states in the United States. Reduced form regression estimates that flexibly control for time trends suggest that a 10 percentage point reduction in mobility is associated with a 0.04-0.09 reduction in the value of the effective reproduction number, R(t), depending on geographical region and modelling choice. According to these estimates, to avoid the critical value of R = 1, easing mobility restrictions may have to be limited to below pre-pandemic levels or delayed until other non-mobility related preventative measures reduce R to a level of 0.55-0.7 in Europe, a level of 0.64-0.76 in Asia, and a level of 0.8 in the United States. Given gaps in data availability and inference challenges, these estimates should be interpreted with caution.