Via Tyler Cowen, https://stanfordreview.org/stanford-bicycles-helmets-masks/:
In April of this year, I witnessed something on the Stanford campus that will be seared into my memory forever: a student on a bicycle, wearing flip-flops, AirPods in ear, going the wrong way through a roundabout in an active construction zone, with no helmet. But like any good follower of science, the student was wearing a disposable blue face mask -- for safety, I guess. I think this anecdote is instructive in understanding the social dynamics that have emerged in the COVID-19 pandemic. Seemingly intelligent and well-rounded people (Stanford students, for example) have adopted bizarre, pointless habits to comport with new expectations about how to "stay safe" -- like wearing masks outdoors -- all while continuing in much more risky behaviors. [...] So, I decided to attempt a measurement to quantify this phenomenon. On Wednesday, September 22nd, in the 1:00 pm hour, I observed 400 Stanford cyclists on Lasuen Mall, a popular campus street for bicycles. I simply noted whether each cyclist wore a mask, a helmet, neither, or both. Here are the final tallies: Total cyclists: 400 - (100%) No mask, no helmet: 195 - (49%) Mask, no helmet: 134 - (34%) Helmet, no mask: 42 - (10%) Mask and helmet: 29 - (7%) That works out to a masking rate of 41% and helmet-wearing rate of 17%.