Tim Cook's fortune is tied to Apple's performance in the stock market.
In 2013, two years after Cook became CEO, Apple updated his compensation plan to include large chunks of stock that would vest if, over a three year period, Apple outperformed two-thirds of the S&P 500, an index tracking 500 of the biggest public U.S. companies.
Apple is up 31% in the last 12 months, and it's outperformed 81% of the stocks in the index, according to reports from Bloomberg and CNBC.