I started to wonder which districts were wealthier and poorer. Fortunately, the UIS puts out the Almanac of Illinois Politics that lists the median family income of each legislative district.
I went through and pulled out all of the Senate districts. Then I sorted from poorest to wealthiest.
Since the average income is just shy of $60,000, any district with a median family income less than that would benefit from raising taxes on family income above $60,000, essentially.
Who are those districts? Here they are.
Interesting, isn't it? Lots of Downstate districts are poor, including Downstate Republican districts. But anecdotal evidence suggests Downstate voters have not yet embraced a progressive income tax, even though it's to their economic advantage. That's a public challenge we progressive tax advocates need to meet.
[Update: typo fixed after seeing it on the front page of Capitol Fax -- thanks Rich/Paul]