For the fifth day of mask mess, we got these:

Mitze et al.

Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach. Institute of Labor Economics (2020).

Originally circulated in June 2020, this provisional paper found that compulsory face mask orders “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 various regions in Germany. Mitze et al. derived those findings by comparing the regions’ actual known COVID-19 cases under the mask mandate with their computer models’ predictions of cases in those regions without the mandates. They created “synthetic” control versions of those regions comprising a weighted average of similar regions with similar regional characteristics but no mask mandates.

Their initial focus was on the region of Jena, the the first municipal region in Germany to order mask-wearing (on April 6), and then on other municipal regions that mandated face masks after Jena but by April 22. Mitze et al. note that “The mask regulations in Germany do not require a certain type” of mask.

Mitze et al. found large effects in reducing the growth rate of COVID-19 infections for Jena (compared with their synthetic control Jena) from being the first to mandate face masks. They found very small effects for the other regions, however. They suggest those very small effects might owe to “behavioral adjustments,” i.e., voluntary mask-wearing taking place in other regions before their own mandates (which then would hide the effects of mask-wearing as measured by when it was mandated). They, therefore, viewed finding even a small effect in the other regions as indicative that mask mandates have very large effects in reducing the growth rate of COVID-19 infections.

They ventured that “We believe that the reduction in the growth rate of infections by 40% to 60% is our best estimate of the effects of face masks.” They wrote in their conclusion, “The most convincing argument stresses that Jena introduced face masks before any other region did so.” Going further, however, Mitze et al. went so far as to “stress that 40 to 60% might still be a lower bound” and even hazarded that the effects of masks on reducing the growth rate of COVID-19 infections “might have been even greater if masks had been introduced earlier.”

From estimating a large effect for the first region to mandate face masks as opposed to a “synthetic” control model, they therefore explained away small effects in other early-mandate regions by suggesting spillover effects from the first region. Then they doubled down by stating a belief the reduction in the growth rate of infections could be 40% to 60%, and then decided that “might still be a lower bound” and then that it “might have been even greater.”

In Appendix C, readers learn that Mitze et al. had abandoned testing four other early-mandate regions. They had found positive results from mask mandates in two of those regions. For a third region, however, they found “very small or unclear” results. As for the fourth, “it even seems to be the case that masks increased the number of cases relative to the synthetic control group.”

Does this study support Cooper’s extreme exercise of power?


Their findings were positive but uncertain, and at best only could support being a first-mover in terms of mandating mask-wearing, which North Carolina was not. They were also based on comparisons with computer modeled results. These aspects offer far too much uncertainty upon which to base an extreme emergency order.

Mitze et al. take a Procrustean approach to their findings, highlighting large results from one region, suggesting smaller results from other regions to be indicative of actually large results, and chopping out of their analysis the regions with “very small or unclear” results or a finding that “masks increased the number of cases.” Such research is unreliable and cannot be the basis of an extreme emergency order.

Rader B et al.

Mask Wearing and Control of SARS-CoV-2 Transmission in the United States. medRxiv (2020).

Posted September 1, 2020, this study conducted serial cross-sectional surveys in June via to look at the association between self-reported mask wearing, social distancing, and COVID-19 transmission, and also “the effect of statewide mandates on mask uptake.” Rader et al. found high self-reported mask-wearing in grocery stores reported in June of 84.6%, and a lower proportion wearing masks while visiting friends and family (40.2%). They found a significant change whereby a 10% increase in self-reported mask wearing more than tripled the odds of controlling disease transmission.

Interestingly, this significant finding was not due to state mask mandates. The study appears to buttress the wisdom of promoting voluntary rather than coerced adoption of mask-wearing. Rader et al. found that “Following state mandates, there was no significant change in mask uptake.” They noted that “The absence of a statistical change in mask wearing two weeks following state-wide mandates highlights the point that regulation alone may not drive increased masking behavior.” Rader et al. noted that another report had “found no substantial effect of mask mandates in conjunction with other interventions.” One reason could be, as they point out, that they cannot disaggregate what other, various preventative hygiene and risk avoidance behaviors people may adopt either with or without mask-wearing.

In conclusion, Rader et al. note the “mixed evidence on the effect of mask mandates” along with “a strengthening body of evidence on the effect of masks” to recommend that “policy makers should consider innovative strategies for evaluating and increasing mask usage to help control the pandemic.”

Does this study support Cooper’s extreme exercise of power?


If anything, this study counsels against state mask mandates as unnecessary and indeed redundant. Rader et al. find “no significant change in mask uptake” from mask mandates. They recommend policymakers instead consider “innovative strategies for evaluating and increasing mask usage” voluntarily. Extreme emergency orders are the opposite of innovative strategies.

Click for more of the Twelve Days of Mask Mess series.