It's useful to compare the Gini index of income inequality. These are 2009-2013 estimates from the Census. The scale goes from 0 to 1 where higher values represent greater inequality. Here are the numbers for the Chicagoland planning area:
Cook 0.4973 (one of the highest in the US - top 5%)
Lake 0.4741 (higher than Milwaukee county)
DuPage 0.4478
Kane 0.4305
McHenry 0.3951
Will 0.3948
Kendall 0.3505 (lowest in IL)
Lake has both very poor and very rich areas, while in DuPage there aren't as many very rich or very poor.
Now look at the vote totals (Clinton-Trump) from 2016 in the same Gini order:
Cook 74%-21%
Lake 56%-36%
DuPage 53%-39%
Kane 52%-42%
McHenry 42%-50%
Will 50%-44%
Kendall 46%-46%
Other than McHenry, the counties line up for Clinton in the same order as their income inequality. Correlation doesn't prove causation, but it's an interesting relationship.
How does Porter County, Indiana (politically 100 percent a “collar county” even if not in the same state) compare? It narrowly voted for Trump, but I have thought that minus Mike Pence on the ballot Hilary would have emulated Obama, who was the first Democrat to win a majority in Porter County since 1852.
