Mask Mandates and COVID-19 Infection Growth Rates

Several government agencies (including the CDC and other federal and state level agencies) have been collecting and creating big datasets around the COVID-19 global pandemic. These data provide important information that can be used to inform our understanding of the effectiveness of different policies and measures in reducing the spread of the virus. In this paper, we explore the relationship between mask mandates and COVID-19 infection rates to try to understand the role that mask mandates play in infection growth rates. Using a difference-in-difference estimation and data from the CDC and other state agencies, the results suggest that mask mandates are associated with a 15% decrease in COVID-19 infection growth rates during the late spring/early summer of 2020. These results are not impacted by differences in population density. Considering Republican controlled states only, masks were associated with a 9% decrease in COVID-19 infection growth rates. Considering states that had stay-at-home orders only, mask mandate were associated with an 18% decrease in COVID-19 infection growth rates. Overall, the results in this paper suggest that mask mandates had a significant impact on reducing the spread of COVID-19 during the late spring and early summer of 2020 in the US.