> Relative to the peers in their own country they usually do

What about people born in the wrong neighbourhood or even the wrong family.

I have a hard time beleiving IQ is a strong predictor of income. Anecdotally I personally know a lot of dumb people who make a lot of money and intelligent people who don't.

If anything I'd say social skills are probably a better predictor of income.

Obviously it's "on average". Of course not every single person will be ranked by their IQ.

I know a 5'3" guy who played in the NBA.