[Pfhreak]

Just a reminder, that tool likely underestimates the risk of covid. Seroprevalence data shows undercounting of up to 24 times (rather than the 5 or 10 this tool shows.)

Also, this tool assumes you are only seeing people from your county.

And humans are terrible at assessing compound risk. If the tool shows a 5% risk from a gathering, people will likely attend multiple events. ("Oh, it's only 5% to go to Thanksgiving. And 5% to go to Friendsgiving. etc.") When you consider multiple events, risk doesn't stay constant.

So while that tool is interesting, don't look at it as a mechanism to say, "Yeah, it's probably ok to have a gathering."

[aroch]

Lead dev here.

While you're not wrong that we might be under-estimating risk, I'll note that we do take into consideration seroprevalence in our calculations (so called, ascertainment bias). We provide estimates for two cases; 5x and 10x under-counting bias.

And you are right, that risk is additive (to a degree) if you go do multiple parties. And people are terrible at doing this sort of calculation. Our messaging, in our manuscript/press/social media has always been to limit gatherings of any size, and mask and gather outside as much as possible

[xur17]

It's also worth noting that this tool shows the risk of at least one other person in attendance having covid before going, not the risk of contracting covid at the event.

[3JPLW]

This is a good resource for thinking around limiting transmission risks:

https://english.elpais.com/society/2020-10-28/a-room-a-bar-a...