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The 50 Top American Philanthropists

How We Create The List: To measure what donors have given or pledged over the past five years, a team of reporters spends months conducting interviews and scouring databases, news reports, and foundation filings. For consistency, we count pledges in full at the time they're announced, discounting only those that are formally revoked. If a gift is in stock, we value it at the time it's announced. To avoid double-counting, the survey counts gifts to foundations at the time they're given and not when the money flows out of foundations.

*Based on public records and interviews with donors **Based on Forbes 400 list and donor information. Data: BusinessWeek, The Chronicle of Philanthropy and the Center on Philanthropy at Indiana University.