According to Wicherts et al. (2010), the average African IQ will markedly increase in the near-term due to the processes underlying the Flynn effect . They show that there has been a steep score increase in the samples that they deem representative.
Is the African IQ really skyrocketing? Is the Congo student IQ really now around 120-something? Using Lynn’s IQ data bank, I plotted the increase in African IQs over time. There is disagreement about several of the sample scores. The graph on the left is based on a minimalistic exclusion criteria with judgement calls made by me. The graph on the right is based on a minimalistic exclusion criteria with judgement calls made by Wicherts et al. The rationale for using the complete data bank is that this presents a better picture of “the African IQ”; sampling bias at either ends (e.g., university students and tribal children) will cancel each other out. The overlap of the African Average calculated using the complete bank and the average derived from international assessments supports this contention. (Note: I used the un-weighted means, so the average IQs are slightly inflated in these graphs. The weighted means were 73.1 and 74.3 for the first and second graph, respectively.)
The regression lines show that the African IQs have been fairly constant across time relative to UK norms. If an accelerated Flynn effect was occurring in Africa, such that the African and Western averages were due to intercept in the near-term, we would expect a positive slope of a more than negligible magnitude. If the Flynn effect had yet to hit Africa, we would expect a negative slope, as the Western scores should have risen over time relative to the African scores. The mysterious Flynn effect seems to have occurred in African in tandem with the West. The massive African Flynn effect found by Wicherts et al. appears to have been a result of sampling bias.
For further confirmation of this, I plotted the international test score equivalents (calculated using equalization of the means) over time (K = 17). Were Wicherts et al. correct, see the figure at the top of the page, the African student scores should show an increase corresponding to their supposed IQ increase. They don’t. Rather, the African student scores show a decrease in tandem with increased enrollment and increased test sophistication.
 Wicherts, 2010. Raven’s test performance of sub-Saharan Africans: Average performance,
psychometric properties, and the Flynn Effect