All of the studies I have ever seen discussed are hopelessly terrible. People like Murray cite apartheid-era South Africa IQ studies, for example, where some of the black children being tested didn't even speak the test language natively. Others look at country differences and claim to extract racial differences from that, as if education and culture play no role in IQ scores. Virtually none of these studies actually look at the genetics of the populations they are testing, they just go by outward aspect, thus making most of their genetic claims laughable. And, of course, many of them are either small samples, p-hacking, or outright fabricated - like many papers in psychology.