As you may know, 60 Minutes aired a segment on Sunday that basically accused Florida Gov. Ron DeSantis of corruption for giving Publix supermarkets a contract to vaccinate Floridians. The evidence for this was all but nonexistent, and conservatives are outraged about the affair.
I don't really blame them. One of the problems is that DeSantis is a high-profile Trumpie with obvious ambitions, and Florida has certainly engaged in some questionable behavior. That makes him a target. Nevertheless, I'm hard pressed to find any good evidence that Florida is a serious outlier in COVID-19 mortality even though DeSantis has kept the state more open than most.
Anyway, this got me a little curious about the impact of mask mandates. DeSantis has never issued a statewide mandate and has recently tried to ban local governments from doing so. How much difference has this made?
First I did some puttering around about the effect of mask wearing in general. It's a very difficult thing to measure because higher COVID rates probably cause more mask wearing, which means a crude study will find that mask wearing correlates with higher COVID rates. It's also the case that people who refuse to wear masks are the kind of people who probably engage in other risky behavior too. Everyone is well aware of this, which means researchers have turned to complicated estimates based on natural experiments, instrumental variables, and tons of controls. The upshot is that there's some evidence that increased mask wearing produces reduced COVID infection rates, but above a certain level the effect appears to be both modest and questionable.
That's not the end of the story, though. Even if increasing mask wearing from, say 50% to 55% has an effect, there's another question to answer: do mask mandates cause more people to wear masks in the first place? There's research from last year that suggests they do, but check out this weird-looking scatterplot from a more recent study:

An eyeball check suggests that mask wearing increases only slightly when a state issues a mask mandate. I used a super-special, completely sketchy method to check this out. Here are the results:

I copied two vertical segments of the chart, one from just before the mandate (left) and one from two weeks later (right). Then I blurred both of them out to form uniform fields and converted them to black and white. The right hand image is lighter, which suggests that mask wearing went up, but only a tiny amount.
The study itself agrees that, on a statistical basis, there's no measurable effect. This means there's basically no evidence that statewide mask mandates produce any behavioral change at all.
This is hardly the end of the story, but it does lean in the direction of suggesting that mask mandates don't work because nobody pays attention to them. Perhaps they did earlier in the pandemic, when they were newer and scarier, but not anymore as people have become more jaded. In any case, if this recent study is correct, the level of mask wearing seems like it's now more related to outside factors (the local level of COVID infections, mask mandates from businesses, etc.) than to a proclamation from the governor.
UPDATE: Sorry, I misread the legend. In the original post I suggested that mask wearing had gone down slightly following a mandate, but it's actually up slightly. However, the effect is so small it's basically not measurable.