It is a nice graph, but there is a risk that it is skewed by the fact that different states are in different phases of the pandemic.
The Northeast green grouping may be in the bottom right because it was hit hard earlier and has stricter laws, so more people there wear masks and more people there are now immune so fewer people will know others with the disease.
This may make the correlation appear greater than it is.
An interesting graph would be one that has the same horizontal axis and a different vertical axis:
“People who knew someone who had Covid in the past”
I suspect past experience with an acquaintance having Covid is a larger driver (than current knowledge) to consistent mask wearing.
Another possible bias in this graph is population density.
If the graph had kept the same horizontal axis and had a vertical axis of “Population Lack of Density: Square Miles per Person,” the graph might look similar.
The areas with low population density (those Western states not on the coast) would still be upper left. The densely populated East Coast states would still be bottom right.
Would we conclude that mask wearing increases population density?
There is correlation, however people in a low density/ low population state are likely to know a larger portion of the state’s population than high density/ high population. So why did they not plot cumulative cases in the last 28 days versus mask wearing?
It is interesting that nobody is below 60% and most daa is in the range 70 to 80% so it can be concluded that most americans are wearing masks in public.
Looking at the source COVIDcast Dashboard | DELPHI and reading the fine print, the people wearing masks is done by a facebook survey as are most of the other stats. So all of this is self reported and likely subject to biases.