IQ is a much better predictor, controlling for other known contributors, of success for individuals within, say, the United States, than it is for countries.

Sure, IQ “correlates strongly” with national economic success, but that’s because of other causal relationships, like that economic success predicts environmental conditions which are known contributors to IQ.

There’s no paradox here.

There is a paradox.

First off IQ only has a slight correlation with individual success past a certain point (someone with below 60 IQ is obviously going to have a hard time succeeding). The data shows that for high IQ and average IQ there is only a slight correlation with success.

Second what you said is patently false. We do not know if there is a causal relationship because a casual experiment is nearly impossible to conduct. This is very different from saying there is "no causal relationship." A correlation points to a possibility of causative relationships. Literally. You make a statement as if it was true, tell me the exact causal experiment you used to determine your statement about "no causal relationship".

Third. The correlation between economic success and IQ is much much stronger then the correlation between individual success and IQ.

Again there is a paradox. You are wrong.

Makes sense. If you're a genius in a country of people who make worse decisions (IQ/culture/other), you may ne worse off than an average person in a country with an average average decision making level

To me it doesn't make sense. Why doesn't this exact same logic apply to individual success?