Maths scores of 15-year-olds in 80 countries and economies
Representative samples of roughly 4,000–7,000 students each, same test, checked translations. This is achievement, not IQ. The right column rescales each mean to IQ-style points relative to that cycle's OECD average (SD about 90), purely to show size.
PISA 2022 figures checked against the OECD Volume I ranking table (Dec 2023). Superseded by PISA 2025, released 8 September 2026. Dark line = OECD average. Some entries are cities or regions (e.g. Macao, Hong Kong, Baku), not whole countries. India, China (mainland) and most of Africa did not take part in 2022.
Lists from online test-takers (self-selected volunteers) and lists built on Lynn-style compilations of old studies give wildly different numbers. Pick a country.
Five steps from a classroom test to a country's IQ
Same studies, different rules, different answers
Richard Lynn and Tatu Vanhanen put together the lists most people still cite, using studies from the early 2000s. Jelte Wicherts and colleagues later went back through sources from several regions. When they used explicit inclusion rules and restored omitted samples, the averages were considerably higher. Critics also questioned whether one small study could stand in for an entire country.
Critics also challenged the authors' hereditarian reading. Later papers that relied on the same datasets have been corrected or retracted, and some journals and professional bodies have stepped away from the work.
Two populations, any gap you like: they still overlap heavily
Groups A and B may have the same SD of 15. Even a wide average gap leaves heavy overlap; variation within a country exceeds the gap.
Documented environmental levers on a population's scores
Ritchie and Tucker-Drob's meta-analysis of natural experiments put the effect of an extra year of education at roughly one to five IQ points.
Ritchie & Tucker-Drob (2018), Psychological Science.Those effect sizes are summaries of the reviews listed below, so consult the original papers before quoting them. During the twentieth century, within-country Flynn-effect gains were often as large as the international gaps people repeat.
International assessments measure something narrower, much more carefully
PISA (OECD, age 15), TIMSS (IEA, grades 4 and 8), PIRLS (IEA, grade 4). They test schooled knowledge and skills, not IQ, but they are the most comparable cross-national cognitive data available.
- Lynn, R., & Vanhanen, T. (2002). IQ and the Wealth of Nations. Praeger.
- Wicherts, J. M., Dolan, C. V., & van der Maas, H. L. J. (2010). A systematic literature review of the average IQ of sub-Saharan Africans. Intelligence, 38(1), 1–20.
- Wicherts, J. M., Borsboom, D., & Dolan, C. V. (2010). Why national IQs do not support evolutionary theories of intelligence. Personality and Individual Differences, 48(2), 91–96.
- Ritchie, S. J., & Tucker-Drob, E. M. (2018). How much does education improve intelligence? A meta-analysis. Psychological Science, 29(8), 1358–1369.
- Qian, M., et al. (2005). The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China. Asia Pacific Journal of Clinical Nutrition, 14(1), 32–42.
- Lanphear, B. P., et al. (2005). Low-level environmental lead exposure and children's intellectual function: an international pooled analysis. Environmental Health Perspectives, 113(7), 894–899.
- Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains: A formal meta-analysis of the Flynn effect (1909–2013). Perspectives on Psychological Science, 10(3), 282–306.
- OECD (2023). PISA 2022 Results (Volume I): The State of Learning and Equity in Education.
- OECD (2026). PISA 2025 Results (Volume I): Future-Ready Students. Published 8 September 2026.