(Editor's Note: This article was published first at Illinois Policy Institute).
Illinois’ population decline hasn’t just affected select areas of the state: New data from the U.S. Census Bureau estimates only four of the state’s 102 counties avoided losing people from July 2019-July 2020. One of those four avoided a loss by gaining one person.
Statewide, the decline in population was driven entirely by people moving out of the state. That was also the primary reason for population decline across Illinois counties.
The largest declines in numeric terms came from Illinois’ most populous counties, with Cook, DuPage and Lake counties seeing large declines. Cook County’s population shrank by an estimated 37,042 in 2020, the second most of any county in the nation, behind only Los Angeles County.
However, the areas shedding population the fastest on a percentage basis were more rural counties across Illinois, with Alexander County shedding population at nearly double the rate of any other county.
While the estimates released May 4 by the Census Bureau offer insights into where population decline is occurring the most, there are discrepancies between the Census Bureau’s estimates of the population and their official decennial Census count, which showed a much smaller population loss that hasn’t yet been addressed by the Census Bureau.
Questions over the accuracy of the official count have been raised on numerous occasions in recent years. One of the primary ways the Census Bureau checks the official count is to compare it with their previous estimates.
It is also unclear what effect Illinois’ increased Census outreach spending, which was second highest in the nation, had on the official results. It is possible increased spending resulted in a more accurate count in 2020 than in 2010, which could explain the difference in the official count from the estimates. The 2020 estimates are based on the 2010 official count.
This wouldn’t be the first time improvements in the Census process have resulted in official counts that are different from the estimates. It is also more likely in this scenario that the estimated geographic trends in population change are still relatively accurate, just that the 2010 base population level was incorrect.
The recently published official decennial Census count pegged Illinois’ population higher than estimates projected, but the population drop of 18,124 residents was still the first time in 200 years Illinois lost population in the official count. No matter the reason for the discrepancy between the count and estimates, the new estimates data still likely provides valuable insight into where changes in the state population are occurring most.
Regardless of the final number, Illinois lawmakers are now tasked with drawing new state and congressional districts, including eliminating one of the congressional districts. The estimates of which areas of the state are losing residents the most could provide some insight into which legislative and congressional districts are most likely to see substantial change.
Congressional redistricting is especially strict, requiring districts as close to equal in population as practical, meaning there is virtually no way to draw districts without the official census numbers. Candidates cannot know what the districts will look like until after the Illinois General Assembly passes a map and Gov. J.B. Pritzker signs it into law.
Because the detailed numbers are not expected to be available until late summer, candidates will be scrambling to gather the required signatures to meet the Nov. 29 filing deadline under the current election code.
No one will know which representative’s district will be eliminated, though with supermajorities in the Illinois House, Illinois Senate and control of the governor’s office, it is a safe bet Democrats will target a Republican-held seat.
The curb on that power had been Pritzker’s long-proclaimed promise to veto any partisan, gerrymandered map. Since Pritzker backed away from that promise and said April 27 he trusted state lawmakers to create a fair map, it is doubtful flawed data and a partisan process can yield much that can be trusted.