Face masks became compulsory in all German federal states between 20 and 29 April 2020. Six regions made masks compulsory before the introduction at the federal level, between 6 and 25 April. This leads to a lag of 2 to 18 days between individual regions and the corresponding federal states. 

The paper compares the Covid-19 development in various regions to their synthetic counterparts, constructed as a weighted average of control regions that are similar to the regions of interest. Structural dimensions taken into account include prior Covid-19 cases, the demographic structure and the local health care system. 

The authors conclude that the daily growth rate of Covid-19 cases falls by around 40% due to mandatory mask-wearing.

Link to the paper here.

Posted by Maria Perrotta Berlin