[sandos]

I mean, there has to be a literal _wealth_ of data on mask efficiency by now, considering the _wildly_ different mask mandates between countries? If they are effective it should be somehow visible in transmission rates or whatever after and before masks became mandated.

Sweden where I live has never had any kind of wide mask mandate in public. There has been rules for public transport where I live, and in the office where I work but we worked at home so. Also recommendations for wearing a mask in shops if you are unable to keep a 2m distance. But I have never seen a majority of people anywhere here wear masks.

[dkonofalski]

There is. The OP even talks about a study done during one of the worst outbreaks of delta and the significant effect it had in Missouri. The same type of change in multiple cities where the treatment (mandate) was in effect occurring while also not happening in the other places where it wasn't in effect? That's not a coincidence anymore.

[stakkur]

For Missouri's study to be valid, statistically and empirically, you'd have to measure the actual wearing of masks in areas with mandates, and control for other factors. Did the Missouri study measure actual mask use, and control for other factors?

[fomine3]

There are no legal mandates to wear mask in Japan, but many shops order to wear mask.