The report came in response to a proposed constitutional amendment that would replace the state's current flat income-tax rate of 4.95 percent with a graduated system where higher rates would apply to higher incomes. By PETER HANCOCKphancock@captiolnewsillinois.com SPRINGFIELD — One of the nation's leading credit rating agencies said Monday that adopting a graduated income-tax system in Illinois probably would provide some much-needed revenue, but whether state's credit rating would be improved depends on how the state uses the new money. read more