Considering that it is designed to measure intelligence in a way that can be objectively defined, I'd say it correlates pretty good. Can you think of many intelligent people with a low IQ or unintelligent people with a high IQ?

Intelligence is not defined precisely enough to speak of correlation here. Maybe a better question to consider is: is it fair that salary is correlated with IQ?

If anyone could answer this question with confidence, it'd be 100%.