Mason  🏃‍♂️ ✂️

The way to view masks is simply as a factor multiplied against the value of R0. If R0 starts at some value like 1.2 that allows numbers to increase, and mask reduce risk of transmission by some amount, say, 30%, R0 is now below 1.0.

So in this way, even a marginally effective mask can be effective enough to reverse growth of cases. People who say " only" 60% effective as if that is simply pointless don't get the way it works.

Same thing is true for vaccine effectiveness or even herd immunity (which kills before it works). They all work by reducing R0

the point is that masks may not in fact reduce R0, if they cause you to act in a way that puts you in close contact with more people, go indoors with more frequency, etc.

They do that only if you assume it changes behavior. We have no proof of that. But we know, ceteris paribus, that there is less transmission with masks. I am unconvinced that the White House acted more or less recklessly due to using masks.

In any case it is just as stupid to say don't use them because it will stimulate risky behavior as it would be to encourage riding motorcycles in flip flops shirtless and with no helmet.

If you're implying I said don't use them you should re-read the part where I said you'd be crazy to not use them.

My point was that a year or two from now I put a non-zero probability on a study showing that mask wearing, the cultural practice, across all 'masks' (not just N95s) had a statistically insignificant effect on R0, or even increased it.