[Symmetry]

First, it is indeed true that modern Germany has a fairly generous social welfare system and you could certainly argue that nobody in Germany is really poor today. But as you might know, during the Cold War Germany was partitioned into two separate countries, and while welfare programs were present back then did exist they didn't actually transfer money between the two countries. And since West Germany was much richer than East Germany, this meant that everyone in East Germany was relatively poor. Back when West Germany was much wealthier than East Germany the inhabitants had higher IQs than East Germans, but nowadays this is no longer true. Hence, evidence that wealth causes IQ differences.

Now, it might be that communism was crushing the hope of East Germans or something. That could also explain this particular difference. But we can measure social mobility and people's beliefs in social mobility across countries and see if it makes a difference. And as far as I can tell it doesn't, since social mobility and believe in social mobility are lower in most places today than they were in 1960, but the Flynn effect[1] continues to march on.

Having beliefs is nice and complex beliefs like those put us humans way above the vast majority of the lifeforms on this planet. But as someone pursing a PhD I would hope that you would examine the implications of your beliefs and test those implications against reality.

And IQ does have predictive power with respect to income[2], though not as strongly as other factors.

[1]https://en.wikipedia.org/wiki/Flynn_effect [2]en.wikipedia.org/wiki/Intelligence_quotient#Income