Average IQ in Illinois: Data, Rankings and What It Means

Illinois is the sixth most populous state in America with approximately 12.6 million residents. Its economic and intellectual identity is almost entirely shaped by Chicago — a city that functions simultaneously as a major financial hub, a world-class university city home to the University of Chicago and Northwestern, and one of the most deeply segregated major cities in America. The state's estimated average IQ of approximately 99.0 places it 18th nationally, but that single number conceals one of the most internally divided cognitive profiles of any state. Understanding what IQ actually measures is essential context before interpreting Illinois's data — because the state's extraordinary intra-city inequality makes the aggregate figure particularly misleading.

This combination of extraordinary intellectual concentration and extreme inequality produces an IQ profile that is more internally divided than almost any other state — with some of the highest-performing neighbourhoods in the country sitting alongside some of the most persistently underperforming.

Illinois National Ranking

Illinois's estimated average IQ of approximately 99.0 places it 18th nationally — just below the national average of 100 but well above the southern states and roughly comparable to other large Midwestern states. The state's ranking reflects the strong pull of Chicago's educated professional class upward against the downward pull of the city's deeply underserved south and west side communities. Research on how IQ tests are scored helps explain why population-level figures like this must always be read as distributions rather than fixed values — especially in a state as internally diverse as Illinois.

Chicago vs Illinois — A Tale of Two Cognitive Worlds

The distinction between Chicago and the rest of Illinois is even more dramatic than the Manhattan vs New York State divide. Illinois outside of Chicago — particularly the rural farming communities of central and southern Illinois — performs at or below national average on cognitive measures. Chicago itself contains extraordinary extremes.

The University of Chicago Effect

The University of Chicago has produced more Nobel Prize winners per faculty member than almost any other institution in the world. Located in the Hyde Park neighbourhood on Chicago's south side, it represents one of the most concentrated collections of intellectual achievement in human history.

Chicago's Segregation and Its Cognitive Consequences

Chicago is consistently ranked as the most racially segregated major city in the United States. This segregation has direct and measurable effects on cognitive development outcomes because it concentrates poverty, underfunded schools, environmental stressors, and limited access to cognitive enrichment in specific geographic areas. The pattern mirrors findings across the broader IQ-by-state research — as explored in the article on average IQ by country, where resource inequality between regions consistently predicts cognitive outcome gaps that are environmental rather than biological in origin.

A 25–30 point IQ gap between neighbourhoods within the same city is one of the most extreme documented in any American metropolitan area. This gap is almost entirely environmentally driven — the result of decades of deliberate policy choices around school funding, housing, and resource allocation rather than any fixed biological difference between populations.

Illinois's Finance and Technology Economy

Beyond its universities, Chicago's status as one of the world's premier financial centres adds a significant professional cognitive anchor to the state's aggregate score. Chicago is home to the Chicago Mercantile Exchange and the Chicago Board Options Exchange — together the two largest derivatives marketplaces in the world — and the analytical demands of derivatives trading, quantitative finance, and risk modelling attract some of the highest concentrations of mathematically trained professionals of any industry globally. The city's financial sector employs tens of thousands of quantitative analysts, actuaries, economists, and software engineers whose professional work is among the most analytically demanding of any occupation category.

Chicago's technology sector has grown substantially over the past decade around the financial technology and enterprise software space. Companies including Morningstar, Grubhub, Narrative Science, and a growing ecosystem of fintech startups have established Chicago as a genuine technology hub — not at the scale of San Francisco or New York, but meaningfully competitive with cities like Boston and Seattle for specific verticals. The Illinois Institute of Technology, DePaul University's College of Computing and Digital Media, and the University of Illinois at Chicago all supply local graduate talent that feeds this growing knowledge economy.

The consequences for aggregate cognitive performance are significant. When a metropolitan area employs a large proportion of its workforce in roles that demand continuous high-level analytical reasoning — financial modelling, software architecture, quantitative research — the evidence on fluid and crystallised intelligence consistently shows that these professional environments actively develop cognitive capacity over time, producing workforces that score measurably higher on cognitive assessments than their educational attainment alone would predict. Chicago's financial and technology sectors function as a sustained cognitive training environment for the tens of thousands of professionals they employ — creating an upward pull on the aggregate that partially offsets the downward pressure from the city's most disadvantaged communities.

Brain Drain from Downstate Illinois

While Chicago's cognitive profile is complex and internally divided, the rest of Illinois faces a more straightforward and chronic problem: sustained brain drain. Central and southern Illinois — the agricultural heartland of the state, historically anchored by Caterpillar's manufacturing operations in Peoria, coal mining in the south, and extensive grain farming across the central plains — has been losing its most highly educated residents to Chicago and other major metropolitan areas for decades.

The University of Illinois at Urbana-Champaign is the state's flagship public research institution and one of the top engineering and computer science universities in the world. Yet the majority of its graduates leave Illinois upon completing their degrees — drawn to technology hubs in California, Seattle, and New York where the demand for their skills commands higher salaries and more dynamic career paths. This export of intellectual capital produced by Illinois taxpayers to other states is one of the most significant structural challenges facing downstate Illinois's long-term economic and cognitive trajectory.

Peoria, once Caterpillar's manufacturing stronghold, illustrates the downstate challenge sharply. Manufacturing decline, population loss, and the departure of educated young residents have left a city whose cognitive and economic profile has deteriorated steadily over the past generation. Springfield, the state capital, has a professional class of government and legal workers that maintains a modest cognitive anchor, but lacks the university presence or private sector knowledge economy to counterbalance the broader downstate trend. The research on working memory and IQ helps explain why economically stressful environments — characterised by financial insecurity, limited cognitive stimulation at work, and restricted access to educational enrichment — tend to compound cognitive disadvantage over time rather than leaving it static.

What Illinois IQ Data Means For You

Illinois illustrates perhaps more starkly than any other state that average IQ is an environmental outcome as much as a fixed attribute. The extraordinary difference between a child growing up in Winnetka with access to one of the best-funded school districts in America and a child growing up in Englewood with chronically underfunded schools is almost entirely the product of policy — not genetics, not culture, not individual capacity.

Whatever state you live in and whatever your starting point, your IQ reflects where you have been as much as what you were born with. The free IQ test at DesperateMinds gives you a baseline score across four cognitive domains in 20 minutes — a starting point for understanding your current cognitive profile and where there is room to grow.