In Illinois, sales taxes only apply to the sale of goods, not services. So you pay 9% on a Big Mac, but 0% on your personal trainer, stock broker, or lawyer.
The Governor tried to address this by rolling out a General Receipts Tax, which would get at some of those services, but he is so inept and politically bankrupt right now that service industries crushed him.
Meanwhile, check this out:
Taking a quick look at census business data:
Top 6 sectors for Cook County (by % of total payroll spending)
13% Professional, Scientific, Tech
11% Health Care
7% Wholesale Trade
6% Management of companies
That means that #1, #2, #3 and #6 of our top sectors (making up 45% of our economy) pay little to no sales tax. Include them, but reduce the rate, and you can get it passed.