The evidence is striking. One study of CEOs of large Swedish companies found that on average they ranked at the 83rd percentile of measured IQ (for CEOs of smaller companies, the rank was the 66th percentile). That’s above average, but it’s hardly a cluster at the top of the distribution. Many CEOs undoubtedly achieved their position through hard work, charisma, people skills and other abilities, not to mention luck.
In the broader distribution, the connection between IQ and income is also positive but underwhelming. One study concluded that moving from the 25th to the 75th percentile of IQ correlates with a 10% to 16% boost in earnings. That may feel significant when you get it, but it doesn’t push you into a whole new socioeconomic class.