— US state cognitive research
Average IQ in Illinois
Published state-level cognitive ability research places Illinois at an estimated average IQ of around 100. These estimates carry wide confidence intervals and should be interpreted as rough population averages, not precise measurements.
Illinois is near the national average with Chicago's concentration of educated professionals offset by lower-performing rural and urban-core areas.
Why state IQ averages differ
State-level IQ differences in the US are largely explained by:
- Educational spending per pupil — states that invest more in K-12 education see higher average cognitive test performance
- Income inequality — childhood poverty correlates strongly with cognitive test performance due to nutrition, stress, and access to stimulating environments
- Migration patterns — states with large educated immigrant inflows (California, New York, Virginia) score differently than net-outflow states
- Industry mix — tech-heavy states attract highly educated workers, raising the state average
- Urban concentration — virtually all states show urban areas outperforming rural areas by 8-12 IQ points
States with similar average IQ
- Average IQ in New Jersey — estimated 102
- Average IQ in Minnesota — estimated 102
- Average IQ in Wisconsin — estimated 102
- Average IQ in Iowa — estimated 101
- Average IQ in Montana — estimated 101
IQ vs educational outcomes
State IQ estimates correlate strongly (r ≈ 0.7) with NAEP (National Assessment of Educational Progress) scores, which are independently measured. This gives the estimates some external validity. The correlation also illustrates that IQ is bidirectional with education — better schools produce higher test scores and better test preparation environments.