A version of this article first appeared in CNBC's Inside Wealth newsletter with Robert Frank, a weekly guide to the high-net-worth investor and consumer. Sign up to receive future editions, straight to your inbox.

In June 2010, Bill Gates , Melinda French Gates and Warren Buffett started what could be described as the world's most ambitious fundraising drive. After promising to give away the vast majority of their wealth, the trio asked their ultra-wealthy peers to pledge at least half of their assets to charity during their lifetimes or in their estates.

In two months, the Giving Pledge garnered signatures from 40 of America's richest families and individuals to sign up. That first batch of pledgers, including Michael Bloomberg and David Rockefeller, was announced 15 years

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