Association of State-Issued Mask Mandates with COVID-19 Case Counts
We have interpreted and extended an analysis published on the US CDC website 5 March 2021, which calculated the benefits of imposed mask mandates. Historical studies of masking in the general population have produced contradictory results with respect to their effectiveness in stemming spread of respiratory viral infections. The CDC study is based on a comparison of Daily Growth Rate (DGR) in number of COVID cases (or deaths) before and after imposition of mask mandates. We show that the downward trend in DGR began before masking and continued after masking. We add controls to the CDC methodology by comparing states that imposed mask mandates to states that did not. We report evidence of short-term benefit for the first 30 days that is lost when DGR increased in the fall more in masked states than unmasked. Overall, we find that the benefits reported by CDC can be completely explained by saturation effects, weather changes, and other factors apart from the government mandates that the study was designed to evaluate.