Billionaire David Rubenstein, co-founder of the private equity firm, the Carlyle Group, discusses why he bought the Magna Carta at Sotheby's on December 19, 2007, in order to keep the document in the United States after he heard rumors of a potential foreign buyer. Rubenstein, also an avid historian, coined the idea of "patriotic philanthropy," which is donating money towards projects that serve some national interest. For example, he has given large sums of money towards the renovation of the Washington Monument and the National Zoo. There are 17 surviving copies of the Magna Carta–15 in Britain, one in Australia, and one in the United States.