Another 17 of America's richest people, including Facebook's Mark Zuckerberg, junk bond pioneer Michael Milken and AOL co-founder Steve Case, have pledged to give away most of their wealth.
They are the latest to join the Giving Pledge, an effort led by Microsoft founder Bill Gates and investor Warren Buffett to commit the country's wealthiest people to step up their charitable donations.
They've now signed up 57 people and their families. The list also includes New York Mayor Michael Bloomberg, CNN founder Ted Turner and film director George Lucas.
Though not a formal contract, those who pledge are committing to give away at least half of their wealth to philanthropic causes either before or after they die.