The Illinois exodus is being felt in the state's largest population center. 

ChicagoTribune - The metro Chicago area lost an estimated 22,068 residents from 2017 to 2018, according to U.S. Census Bureau data released Thursday. While New York and Los Angeles also shrank, the Chicago region saw bigger decreases both in total numbers and in percent change; the area lost 0.23 percent of its population, more than twice New York’s 0.10 percent.

The fact that Chicago saw a bigger drop in population than other major cities in the country shows that this is an Illinois problem, not necessarily a national trend.

Chicago Tribune

 

That graph shows the other effect the Illinois exodus has produced. Usually, the collar counties of DuPage, Kane, Lake, McHenry and Will see some growth when Chicago's population declines, that isn't the case over the past decade.