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Half of the American population has an IQ above 98 — and half is below it. That's the headline answer. But the average IQ in the US is more nuanced than a single number, and the trend over the last decade has surprised researchers.
Current cross-national IQ data places the US average at approximately 97–98, depending on which dataset you use (Lynn & Becker 2019, updated by recent NWEA testing data). This is slightly below the international "norm" of 100, which is set by the highest-performing OECD countries.
That number sounds disappointing, but the methodology matters. Different studies use different test batteries, age cohorts, and norming years. The most defensible US adult IQ estimate sits in the 97–100 range.
State-level data (extrapolated from NAEP and SAT/ACT performance) shows a roughly 8-point spread:
| Tier | Approx. State IQ | Example States |
|---|---|---|
| Highest | 102–104 | Massachusetts, New Hampshire, Minnesota |
| Above average | 100–102 | Vermont, Connecticut, Iowa |
| Average | 97–100 | California, Texas, New York |
| Below average | 94–97 | Mississippi, Louisiana, Alabama |
These differences correlate strongly with educational investment, poverty rates, and lead exposure — not anything intrinsic about the populations themselves.
For most of the 20th century, average IQ rose ~3 points per decade across developed countries — the Flynn Effect. Since around 2005, US IQ scores have plateaued and modestly declined. Researchers attribute this to:
In the most recent global rankings, the US sits roughly 25th–30th by national average IQ. Top scorers include Japan, Singapore, Hong Kong, South Korea, China, Taiwan, and Finland — typically averaging 102–106. The US average IQ is comparable to Australia, France, and the UK.
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Roughly 97–98, depending on data source. The international norm is anchored at 100, so the US sits modestly below the global "ceiling" set by top-performing countries.
Modestly, since around 2005. This "reverse Flynn Effect" is documented in the US, UK, and several Nordic countries — though the size and causes are still debated.
Massachusetts and New Hampshire consistently top state-level rankings (estimated 102–104), driven largely by educational attainment and economic factors.
The US ranks around 25th–30th in global averages, comparable to Australia and the UK, behind East Asian countries (102–106) and Finland.
Anything above 100 is above the international average; above 115 puts you in roughly the top 16% of US adults.
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