Warren Buffett has carried his philanthropy to a new extreme and, in the process, sparked a revolution in the world of giving. Through his launch of the Giving Pledge in June 2010, a joint venture with his partner-in-patronage Bill Gates, Buffett has unlocked billions of dollars for philanthropic causes.

The Pledge itself is radical in its simplicity. Its Signers have to be billionaires. And they have to promise to give at least half of their fortune to charity during their lifetimes.

So far, 69 billionaires have signed the pledge, representing more than $150 billion in philanthropy. That number is "far more" than he and Gates expected, Buffett says. The signers are wildly diverse in their politics and causes—ranging from fighting cancer and funding Jewish schools to housing orphans in Africa and helping farmers in Appalachia.

Still, they are united in their mission: to inspire the world's wealthy to give a Larger percentage of their wealth to charity. It is the world's largest fund-raiser.

"What I'm hoping is that young people 20, 30, 50 years from now might be influenced," Buffett says. "The hope is that our larger population ends up giving a larger proportion of their income to fund philanthropy."

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