Evidence ledgerAvailable measures
Every card keeps the measure, year, method, and limitations attached to the number—or explains why no number is shown.
99.4published estimate points (M=100, SD=15)
Pesta 2022 published state IQ estimate
A research-derived state aggregate standardized to mean 100 and standard deviation 15, not an administered statewide IQ test.
Method and limits
Pesta standardized PIAAC literacy/numeracy and 2015, 2017, and 2019 NAEP reading/math state scores, derived separate PIAAC and NAEP estimates, and averaged them.
- This is an ecological proxy built from achievement and adult-skills assessments, not a representative IQ test of every resident.
- The source populations, years, constructs, and sampling frames differ.
- Do not infer an individual's ability from a state aggregate or treat small state differences as precise.
Uncertainty: The article reports a point estimate but does not provide a state-specific confidence interval in Table 2.
277NAEP scale score
NAEP 2024 grade 8 mathematics average score
Official public-school grade 8 mathematics average on the NAEP 0–500 scale. Reading and grade 4 series remain separate in the source and are not averaged here.
Method and limits
NCES reports results from nationally representative samples using common NAEP assessment frameworks.
- NAEP measures educational achievement and is not an IQ test.
- Grade, subject, accommodations, exclusions, and sampling error must remain visible.
Uncertainty: Pinned as the rounded NCES average for one grade/subject series. Sampling error and other NAEP series are not shown in this single number.
266PIAAC literacy scale score (0–500)
PIAAC adult literacy average score
NCES small-area literacy estimate for adults ages 16–74. Numeracy for Illinois is 252 (credible interval 247–256). Literacy and numeracy are not IQ.
Method and limits
NCES combines 2012/2014/2017 PIAAC survey data with ACS auxiliary data to produce state small-area estimates.
- Small-area estimates are modeled, not direct tests of all state residents.
- Literacy and numeracy are distinct skills and should not be collapsed into IQ.
Uncertainty: 95% credible interval 262–270 from the NCES Skills Map comparison charts.
39.2percent
ACS 2024 bachelor's degree or higher, age 25+
Official survey estimate of the share of adults age 25 and over with a bachelor's degree or higher; included only as educational context, not cognitive ability.
Method and limits
The Census Bureau weights ACS survey responses to estimate population characteristics.
- Educational attainment is not cognitive ability.
- ACS estimates require margins of error and exact table universes for valid comparisons.
Uncertainty: ACS estimates have margins of error. This snapshot pins the FRED GCT1502 percent for the 2024 ACS 1-year release.