[linuxguy2]

Beware density/heat maps that mostly just match population maps. Of course, xkcd has been there before: https://xkcd.com/1138/

[natdempk]

Did you look at the referenced links?

None of them suffer from this problem. Almost all of the charts aren't even density maps, and of the two that are, they are charting family income vs. soil lead level, which wouldn't suffer from the problem mentioned in the comic.