Part of the point of the Wicherts papers was to refute the Lynn data, observing that even taken on its own premises Lynn's team pretty clearly excluded data unfavorable to the conclusion they wanted to draw. But look at Wicherts 2009, at the samples they're talking about. One of the largest was 800 students in Nigerian high schools (a test arranged by IQ researchers to for a cross-cultural comparison, back in 1981). Lynn's data includes, and is materially influenced by, a sample of
59 Senagalese children who were tested while recovering from malaria. The malaria thing is just funny, but it's the numbers that stick out to me.
I'm not getting further into the details here because the easiest-to-understand point here is that there are not in fact programs to generate reliable "average IQ" numbers in different countries. I am struck by the fact that message board nerds from America believe these programs exist, when almost none of us have ever taken an IQ test.