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The tables that circulate as national IQ figures come from one compilation built out of whatever studies existed, in whatever years, on whatever samples. Several of the numbers were estimated rather than measured.
The chart is familiar: a world map shaded by average IQ, or a league table with a country at the top and a country at the bottom. It gets reposted constantly, usually with no source attached. It is worth knowing where it comes from, because the answer explains almost everything about how much weight it can carry.
The tables descend from a compilation assembled by Richard Lynn and Tatu Vanhanen, published in book form in the early 2000s and revised several times since. The method was to search the literature for any study reporting IQ test results in a given country, convert the results onto a common scale, and enter a figure per country.
That is a literature compilation. It is not a cross-national survey. Nobody designed a sampling frame, drew a representative sample in each country, or administered one instrument under matched conditions. The dataset is a summary of whatever research happened to exist, which means its quality varies by country in exactly the way research funding does.
These do not average out. They compound, and they compound unevenly: the countries with the thinnest research literature are precisely the ones whose entries rest on the smallest samples or on imputation.
A number that was estimated from a neighbouring country reads, in a table, exactly like a number that was measured.
The dataset has been criticised in the peer-reviewed literature on methodological grounds — sample quality, the handling of missing data, the comparability of instruments and the interpretation of cross-national differences. Those critiques are technical rather than rhetorical, and they are the reason the dataset is not treated as a standard reference in psychometrics the way, for example, an assessment programme with a published sampling design is.
There is a separate and much larger argument about what any real national difference would mean if it were measured cleanly, involving nutrition, disease burden, schooling, literacy, test familiarity and the age at which populations begin formal education. That argument is worth having on good data. It cannot be settled on this data.
The same caution applies one level down, to your own number. A score means something when you know which scale it sits on, which reference sample the percentile is computed against, and how wide the confidence range around it is. Without those three things a figure is a decoration — whether it is on a world map or on a certificate.
Find your IQ score now! →None of this means cross-national cognitive research is impossible or illegitimate. It means the specific tables in circulation are a compilation of uneven studies with imputed gaps, presented with a precision the underlying data cannot support. Treat a national IQ ranking the way you would treat any chart with no error bars and no methodology section: as a claim, not a measurement. We publish the country figures themselves because people look for them, and this piece is the caveat that belongs beside them.
Overwhelmingly from one compilation of published studies assembled by Richard Lynn and Tatu Vanhanen and revised over subsequent editions. It gathers whatever research existed per country rather than surveying countries under a common design, and where no study existed some values were estimated from neighbouring countries.
The more accurate statement is that they are not precise enough to rank with. The contributing studies differ in test, sample and decade, several entries were imputed rather than measured, and no standard errors accompany the figures — so the small gaps that make a league table interesting are exactly the gaps the data cannot resolve.
Not for IQ. For school subject achievement, programmes such as PISA and TIMSS publish cross-national comparisons with documented sampling, a common instrument and technical reports. They measure something different from IQ, and that difference should not be blurred — but their design is the standard any credible cross-country comparison has to meet.
Corrections: spotted an error? Email corrections@iqmetrics.org and we will update this story and note the change here.
Average scores climbed for decades, then flattened and in places slipped. None of it shows on a score report, because every test is reset so the average is 100 again — which is why a 1990 score is not a 2026 score.
On the scale most modern tests use, 120 sits around the 91st percentile. Change the scale and the same number moves. Add the measurement error every test carries and it stops being a point at all.
Our IIF-certified assessment reports your score with its scale, percentile and confidence range — and a breakdown of the cognitive domains behind it.
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