evidence: Little information is available on a global scale. However, an analysis of the socio-economic determinants of Covid-19 mortality across countries demonstrated that a longer duration of mask wearing by the public was negatively associated with mortality52. In this study, the effect of mask wearing is proxied by the delay between the first infected case and a government recommendation on mask wearing by the public. This study finds that ’in countries with public policies and cultural norms supporting public mask-wearing, per-capita coronavirus mortality increased on average by just 15.8% each week, as compared with 62.1% each week in other countries’. [...] We also found a statistical negative impact of mask wearing on fatality rates with a longer lag. Here, we consider 14- and 28-day lagged variables for illustration (Table 3). We also document that the mask effects on deaths for 7 days after are not reported since this effect is not significant. This insignificance is a proof of credibility of our results since the mask has no effect on fatalities at a very short run horizon (Placebo test). The mask use effect on fatalities for a very large horizon (42 days) is also not significant.