The Medium Run Impact of Non Pharmaceutical Interventions. Evidence from the 1918 Flu in US Cities

Abstract

This paper discusses the impact of Non Pharmaceutical Interventions (NPIs) used during the 1918 pandemic on local death rates and city growth. First, I estimate the impact of Non Pharmaceutical Interventions (NPIs) as school closures and social distancing on the mortality rate on the medium run in 43 US cities. I show that if the death rate is lower in 1918 it becomes larger during the two next years, probably because the herd immunity is lower, reducing the net benefits of the policy. Second I investigate the impact of NPIs on cities dynamics. I don’t find any significant association between city’s growth and the implementation of NPIs. In a nutshell the results suggest that if NPIs might lower the fatality rate during the pic of the pandemic, their health benefits are fragile on the medium run as cities remain more sensitive to diseases in the following years. This suggests that the optimal policy responses to pandemics should also account for herd immunity.