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Billionaire peer pressure: Behind the Buffett-Gates challenge

Bill Gates, Melinda Gates, and Warren Buffett are asking the nation's billionaires to pledge to give at least half their net worth to charity, in their lifetimes or at death. If their campaign succeeds, it could change the face of philanthropy.

So as 2010 arrived, a pledge became the strategy. The idea of aiming for a 50% slice of net worth was pragmatically pulled from the sky, being less than the principals would have liked to ask for but perhaps as much, at least initially, as they can get. The pledges, meanwhile, were never envisioned as legal contracts but rather moral obligations to be both memorialized in writing and taken very seriously. They are in fact to be posted on a new website, givingpledge.org, whose construction Melinda Gates oversaw.

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