If Apple’s stock outperforms the market over the next 8 years, Cook will be able to keep all of the 1 million Apple shares the company promised him back in 2011, which he was previously set to get no matter how Apple’s stock fared. But if Apple’s stock does a lot worse than the market, Cook could lose up to 40 percent of those shares.
Apple says that the changes were made after "outreach discussions this year with many of our largest shareholders". Cook isn't the only one who is having his compensation changed, the company is changing the way it gives out bonuses for all of its top executives.
Cook is reportedly "leading this initiative by example". There is no upside to his new compensation package. At the most he can get the same shares he was promised back in 2011. Apple says it wanted to put less of his shares at risk "because Mr. Cook faces only downside risk from the modification." However, he “expressed a strong desire to set a leadership example in the area of CEO compensation and governance and requested a larger at-risk percentage.”
Cook's million shares were worth $376 million when they were granted, they peaked at $705 million, and at today's stock price they are worth around $413 million.