In 2002, Lynn and Vanhanen produced a dataset which claimed to provide average ‘national IQs’ for nation-states worldwide. Despite extensive critique, this dataset, and subsequent updated versions, have been used in many empirical publications. Here I evaluate the latest version, produced in 2019 by Lynn and Becker, and show that this dataset is not fit for purpose. The primary data sources are inadequate for calculating ‘national IQs’. Most data originates from samples which are wholly unrepresentative of their national populations. Many are convenience samples with small sample sizes, collected over a wide date range (the oldest from the 1940s), often including only children and often including individuals selected because they had particular characteristics (i.e., were deliberately chosen to be unrepresentative). The transformation of cognitive test data from these sources into ‘national IQs’ involved a series of questionable assumptions and arbitrary adjustments. Some of these assumptions were based on Lynn and Becker’s prior beliefs about intelligence, including that regional and racial differences in IQ exist. These methods will result not just in error in the dataset but systematic bias. Even if representative data and appropriate methods were available for constructing ‘national IQs’, it is impossible to generate comparable measures of cognitive ability from culturally diverse populations across the globe. ‘National IQ’ datasets therefore do not provide comparable, accurate and unbiased measures of cognitive ability worldwide, and should not be used to draw inferences about global variation in intelligence.
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Rebecca Sear (2022) studied this question.