"Illinois’s tax system earns it the dubious distinction of placing it on the list of the “Terrible Ten” most regressive states in the nation. Even before federal deduction benefits, it asks families in the bottom 20% of the income scale—to pay 2.3 times as great a share of their
earnings in taxes as do the wealthy. By the same measure, middle-income families in Illinois pay 1.8 times as high a share of their income in taxes as the wealthiest families.
“Illinois is one of only six states nationwide that levies a flat personal income tax,” McIntyre said. “The lack of a progressive income tax to offset regressive sales and property taxes is the
most important factor in making the Illinois tax system so regressive....
Tax Regressivity Worsened Since 1989
The study also examined the impact of changes in the regressivity of Illinois taxes since 1989, when the last cycle of state government shortfalls began. The study’s findings include:
# Tax burdens rose very significantly on low- and middle-income families and slightly on high-income families.
# The main causes of increased burdens were regressive rises in sales and excise taxes.
“Not only is the Illinois tax structure regressive, it got significantly worse in the last decade,” said McIntyre."
http://www.itepnet.org/wp2000/il%20pr.pdfTherein lies the trouble, IMO, it's pretty hard to reach across party lines and do something progressive, like make state taxes more progressive.