IL business formation is composed of self-employed individuals (non business employers with no employees) and employer firms. Best estimate for 2025 is that IL has 1.4M businesses.  The 1.4M enterprises are a vital source of tax and other revenue for both state and local government.   Per Grok

IL has steadily lost employers for more than a decade.   Here is some recent data. 

Granted, that there are likely a number of reasons for a firm to leave IL for another state.  Here is a record of moves related to taxation.

The Chicago area is the heart of the business community of IL.  In 2015, there were 54k+ businesses operating in Chicago.   Today there are 44k+, a decline of 20%.  Consider the implications of business and job losses on the Magnificent Mile, the showcase of retailers.  A loss of 51% of business licenses over a ten year period.  Watertower place, a flagship store on the Magnificant Mile, has a vacancy rate of 30%.