To what extent face masks actually mitigate the spread of the coronavirus is a strongly debated issue in many countries, and the WHO only recently updated their recommendations. After some reluctance, Germany made wearing face masks mandatory in places where physical distancing is difficult, including public transport and stores. Some cities and regions introduced face masks several weeks before the nationwide implementation.
A new IZA discussion paper by Timo Mitze, Reinhold Kosfeld, Johannes Rode and Klaus Wälde exploits this regional variation using the synthetic control method to estimate the face mask effect. Depending on the region analyzed, the study finds that face masks reduced the cumulative number of registered COVID-19 cases between 2.3% and 13% over a period of 10 days after they became compulsory.
In Jena, the first German city that made face masks mandatory, the number of COVID-19 cases fell by 25% over the first 20 days, with a drop of more than 50% among older people aged 60 and over. Estimating the effects for other regions and assessing the credibility of the various estimates, the authors conclude that face masks reduce the daily growth rate of reported infections by around 40%. Based on their findings, they suggest that wearing face masks may be a comparatively cost-effective measure to keep infections low.