( RE: http://www.sciencedirect.com/science/article/pii/S0160289615001300 )
Across the last two decades ? 40% of CEOs were on the top 1% of cognitive ability. Even within CEOs, education/ability was associated with company gross revenue. Becoming and performing as CEO can be considered a difficult mental test battery.
(I want to add that above the upper 1% line, men vastly outnumber women, which is why men vastly outnumber women in all extremes of life.)