Philanthropic Sleuthing

The motto of many of our biggest givers seems to be this: "Tis often better to give than to receive any press about it." Many of America's most generous philanthropists work hard to keep their gifts quiet. Public information on giving is spotty and often out of date. And stocks can be volatile, so large pledges of shares can shift in value over the years.

To compile the most accurate ratings, the team behind BusinessWeek's annual survey relied heavily on news reports, foundation filings, online IRS filings, and interviews. Resources included The Chronicle of Philanthropy, the Forbes 400 Richest Americans, nonprofit GuideStar's online database of IRS foundation filings, and countless other sources. Using this data, we ranked the 50 Most Generous Philanthropists by what they've pledged and given in the past five years. We also estimated their lifetime contributions and presented these figures as a percentage of each philanthropist's net worth.

We count pledges as well as cold hard cash or shares of stock. We believe donors who vow to give their fortunes away in the future deserve to be lauded, not only for their generosity but also because they often inspire others to greater charitable efforts. Still, valuing such pledges can be tricky. In many cases, the actual gift amount changes after the pledge is made. And sometimes philanthropists struggle to make the payments. For consistency, we counted all pledges at their value at the time they were initially announced. We discounted only those that had been formally revoked.

We may have missed some big gifts that donors preferred to stay mum about. But our ranking nevertheless captures the collective generosity of givers who have risen to the challenge of making a difference with their charitable dollars.

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