> IQ scores in most of the Western world began reversing sometime from the 90s to early 00s. [1] That link is for the US but similar stuff has also been observed in most of every Western/OECD nation.

I wonder to what extent demographic shifts account for the observed reversal? It would be interesting to tease out what happens where composition remains constant, i.e. Poland. Though I doubt this explains the entire effect.

> By contrast they're still rapidly increasing in the 'Global South'.

seems like the Flynn effect doing its thing just as it did in western countries in the 20th century.