Another possibility is better disease survival due to increased vitamin D levels from sunshine (or due to some other physiological effect of sunlight).
The effect seems rather large for this to be the explanation, but it sure would be great if a bit of sunlight is all that’s needed!
Maybe in northern states.
But I doubt that vitamin D levels are increasing in the southernmost cities, where heat is likely driving people indoors. Those are the areas that most need explaining.
Another possibility is better disease survival due to increased vitamin D levels from sunshine (or due to some other physiological effect of sunlight).
The effect seems rather large for this to be the explanation, but it sure would be great if a bit of sunlight is all that’s needed!
Maybe in northern states. But I doubt that vitamin D levels are increasing in the southernmost cities, where heat is likely driving people indoors. Those are the areas that most need explaining.
More sunshine in that these are sunnier places and also sunnier times of year, so you get it two ways.