Illinois Undercounted in 2020 Census, Actually Grew to 13 Million — The State's Largest Population Ever

Illinois suffered significant undercounting during the 2020 census, leading to the mistaken conclusion that the state lost residents over the previous ten years — when in reality it added more than a quarter of a million people and swelled to its largest population ever.

That’s the stunning revelation from a report the U.S. Census Bureau itself released on Thursday, admitting that its ten-year head counts were off in more than a dozen states.

Illinois’ purported population loss has become a talking point for everyone from former residents justifying their departure to political candidates using it to bash incumbents for policies they say are prompting a stampede out of the state.

The expectations of population loss in the state were so ingrained that experts had feared a doomsday scenario of losing two congressional seats as a result of the once-a-decade count — rather than the one seat Illinois did lose.

While the release of Thursday’s report does nothing to reverse that loss of political representation in Washington, the finding that the state actually gained more than 250,000 residents between 2010 and 2020 does give Democrats ammunition to try to shout down many of those talking points.

Missing more than 250,000 Illinoisans is roughly the equivalent of not counting anyone in Aurora — Illinois’ second largest city — and the entire downstate city of Decatur.

Gov. J.B. Pritzker cheered the news that put Illinois’ population above 13 million for the first time ever.

“These latest numbers from the U.S. Census Bureau show that Illinois is now a state on the rise with a growing population,” Pritzker said in a statement.

“While it is disappointing that these numbers were not reflected in the initial count, I have already spoken to members of our congressional delegation and will work tirelessly to ensure Illinois receives its fair share of federal funding.”

The governor added that he’s looking “forward to celebrating this development with all Illinoisans, including those who routinely badmouth our state” — a shot at Republican rivals who for years have hammered the state’s Democratic leadership over the loss of population in recent decades.

In a statement, Illinois House Speaker Emanuel “Chris” Welch said the corrected count “confirms what Democrats have been saying all along: Illinois is growing, Illinois is thriving, and Illinois has so much to offer.”

Illinois Senate President Don Harmon, D-Oak Park, added “we need more people cheering for Illinois and fewer spelunking for misery.”

GOP leaders in the General Assembly could not immediately be reached for comment.

The bureau released its findings in its 2020 Post-Enumeration Survey Estimation Report, which is used to determine how accurate its decennial count was. This latest report doesn’t replace the original 2020 census figures.

But it concluded that six states actually experienced undercounts: Arkansas, Florida, Mississippi, Tennessee, Texas and Illinois. On the flipside, eight states were overcounted: Delaware, Hawaii, Massachusetts, Minnesota, New York, Ohio, Rhode Island and Utah.

Illinois’ population was undercounted by nearly 2%, a miscalculation that will have long-term implications.

Since the 2020 census incorrectly reported Illinois lost over 18,000 residents — or a drop of 0.14% — the state lost a seat in the U.S. House of Representatives, something that has happened every census since 1970. The initial 2020 census reported Illinois’ population was 12,812,508.

With the actual growth of about 2% — or more than 250,000 people — it’s still unclear if the state would’ve maintained its 18 seats in Congress or not.

“It is unlikely that that undercount for the 2020 Census would have an effect on the total number of congressional districts as district allocation is based on Illinois population relative to other states,” said Chaundra Van Dyk, project manager with Change Illinois, a left-leaning political advocacy group.

“It would require much more analysis into the states with overcounts and undercounts to say for certain if it would have allowed for Illinois to maintain 18 congressional seats.”

But either way, subsequent statistical sampling from the census, such as Thursday’s determinations of over- and undercounting, can’t be used for reapportioning seats in Congress, thanks to a Supreme Court ruling in 1999.

But the new figures will at least help usher in additional federal funding that the state nearly lost out on.

Laurence Msall, president of the budget watchdog group The Civic Federation estimated the state could receive at least $100 million in additional federal funding based on the new population data.

“So many of our formulas are based on population,” Msall said. “This is really good news for Illinois.”

The coronavirus might have indirectly helped keep the undercount from being even worse, said Rob Paral, a senior researcher with the Great Cities Institute at the University of Illinois Chicago.

He credited community groups knocking on doors and thinking of creative ways to inform people of the 2020 census in the midst of a pandemic with ensuring that many people were counted.

 “I can say that the undercount would have been even worse if Illinois had not had a substantial outreach program,” Paral said. “The state really invested well in my opinion.”

Jay Young, executive director of Common Cause Illinois, said the undercount was to be expected due to the public health crisis and former President Donald Trump’s attempts to disrupt the census.

“We had the former administration working to undercut the efforts of the census bureau and people were rightfully scared,” Young said. “People were scared to open their door in fears of getting sick or in fear of a [U.S. Immigration and Customs Enforcement] agent on the other side of the door.”

Young said it isn’t quite clear how this will generate additional funding and stressed that those undercounted are still most vulnerable.