How risky are protests?
I got to thinking about this today, so I made a rudimentary model to see how much of a risk a couple hundred people getting together are.
First, I made a conservative model that only about 0.5% of people are infected. I ran a simulation of 200 random people getting together 10000 times.
The results were that about 37.3% of "protests" had no COVID-19 infections present. However, another nearly equal 36.84% had one infection. Around 18% had two infections, and the remaining 7% had three or more.
If we just increase that to 1% of the population being infected we end up with only 13% without an infection present, 27% with one, 26.5% with two, and the rest with three or more, and a few with as many as nine.
Let's go one step further and say that 5% of the population is infected. You end up with 1 event with no infections. That's 0.01% of gatherings with more than 200 people NOT having a COVID-19 infection present among them. Indeed most, close to 94% have more than five and some have over 20.
Now, these were random draws and if I ran it again I would expect to get slightly different results. However, with 10,000 simulations I feel very confident that the numbers would be close for each run of the Monte Carlo. If also make the assumption that there isn't a reason that infected individuals would be more of less likely than anyone else to attend a protest. This is probably not true since some number of infected will be symptomatic and more likely to stay home. However, given that I believe the true number of infected to be pretty high, I think these numbers are reasonable to assume possible for asymptomatic or presymptomatic infection rates among the general population.
This doesn't just apply to protests either, it would apply to grocery stores, restaurants, bowling allies, etc. Anywhere that 200 people could gather is applicable here. So, take it as a good reason to strictly limit your time outside the house as much as possible.
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