No. There is essentially no credible research anywhere that ranks countries like this. People are usually citing Richard Lynn's "IQ and the Wealth Of Nations", which has a risible methodology; that paper gives India an 82, not a 77, which is interesting only to the extent that it muddies the waters of where this author got that absurd claim from.

Any time you see a country => IQ mapping somewhere, you should assume you're getting worked. Lynn's work is the most credible attempt at that, and nobody even a little bit serious takes it even a little bit seriously.

Stipulating that it's even possible to produce this kind of ranking, and that it would be meaningful, your answer: because reliably generating the data you would need to do it is a ludicrously expensive proposition. It is a little wild that people sort of automatically buy the idea that Richard Lynn had access to the data he would have needed to perform this analysis!

IQ tests have been around for over 120 years now, haven't they?

I haven't read Richard Lynn's books before, looks like I should check them out, if for anything to see what's going on there.

When I visited "developing" countries, there is for sure something going on (or not going on) there. IQ seems to be a factor, probably due to a lack of nutrition. Or maybe it's a more spiritual thing. Whatever it is, a study based on quantifying the difference is only so helpful either way. While I don't quite know what I saw while I was there, I know that I saw it.

Not interested, sorry, just answering your question.