Illinois may not be losing population after all.
An undercount in the 2020 census missed 46,400 Illinois residents living in group homes, an adjustment to the population base that will be incorporated in future surveys, the state announced Wednesday.
While the total won’t be added retroactively to previously reported census data, the bolstered base may more than offset the nearly 33,000 people Illinois lost in the 2023 annual census update published last month.
“I’m pleased that the Census Bureau has recognized the undercounting that I and many members of Illinois’ congressional delegation have worked to remedy since the 2020 census results were first released,” Gov. J.B. Pritzker said in a news release. “This correction will bring in millions in additional federal funding for crucial programs and help to ensure future counts reflect the true number of Illinois residents.”
State legislators have been calling for a recount of the 2020 census since its initial release, which showed a population of 12,812,508, a decrease of 18,000 people over a decade — the first such decline since Illinois joined the union. A 2022 follow-up survey found the state’s population figures had likely been undercounted.
The 2020 census provides the population baseline used for annual updates until the next decennial survey in 2030. Resetting that number could boost Illinois’ population for the remainder of the decade.
In September, the state, working with the research organization NORC at the University of Chicago, filed a request with the Census Bureau for an official Post-Census Group Quarters Review of the 2020 survey.
Group quarters include everything from nursing homes and college dorms to correctional facilities.
The census review, which was completed Dec. 29 and received by the state this week, found that 733 group quarters were missed or undercounted in the 2020 survey, identifying 46,400 people that should have been included in the Illinois population count.
California and Texas were the only other states to file for a group quarters review.
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Illinois has a lot at stake in finding every resident, with population estimates used to determine the distribution of over $675 billion in annual state and federal programs. The state also lost one congressional seat based on the 2020 census, reducing its representation in the U.S. House from 18 to 17 members.
State representation will be reassessed in 2030, based on population totals from the next decennial census.
The 2023 annual census update, released in December, showed Illinois as one of only eight states to see its population numbers fall last year. The state reportedly lost 32,826 people between July 2022 and July 2023, trailing only New York and California in total population decline. Illinois maintained its ranking as the sixth most populous state at 12,549,689, according to the update.
The Illinois population decline was primarily due to the net domestic migration of 83,839 people who left for other states, offset by net international immigration, which added 40,492 people, according to census data.
While the state found an additional 46,400 residents missing from the 2020 census, the adjustment won’t come into play until the 2024 annual census update in December. The increased 2020 Illinois population base will also be incorporated into annual county and city updates beginning in March, according to the Census Bureau.
The state plans to pursue additional opportunities to appeal and review potential population undercounts in the 2020 census results, a spokesperson said Wednesday.