It isn't especially difficult to find evidence. A very easy search throws up this pdf which reviews a lot of the literature on this particular topic. I have only skimmed it myself as I am too busy, but will probably read the complete thing this weekend as it does look very interesting. I understand that some people might try to use the data for bigoted purposes, but at the end of the day, all I care about is if something is true or not. It serves no greater purpose to stick ones head in the sand and pretend that something does not exist because it might be divisive. That is where I struggle with political correctness. I don't think we should be politically correct when it comes to science. I think it is also very important when you consider how we are opening borders to pretty much everyone. The reality is that you are going to end up with problems if you are not going to be realistic about cultural and intelligence differentials. I think the ignorance of such evidence is partly what is leading to Europe having such a murky time of it today. This is one area where I think Molyneux is quite brave and I think others like Sam Harris and Jordan Peterson have referenced similar things.

https://www1.udel.edu/educ/gottfreds...sen30years.pdf