Jonathan Wai, a research scientist at Duke University and part of the school’s Talent Identification Program, looked at the world’s billionaires and global elite… The global elite—defined by media lists and culled from the attendees of the annual World Economic Forum gathering at Davos, Switzerland—are also highly educated. More than half of Davos attendees went to elite colleges… Harvard, the study suggested, is the top billionaire-making machine. Among U.S. billionaires, more than 1 in 10 went to the school, and globally about 1 in 20 billionaires went there.  As Wai told … : “I was surprised by the extent to which elite schools within each country tend to serve as influential filters for who ends up as a member of these groups of the global elite, specifically the overrepresentation of people who had attended Harvard University” … But wealthy children can also get into top universities in part because their parents attended or gave the school large gifts. Wai acknowledged that “some students attend an elite school with lower-than-typical test scores due to athletics, legacy status or political connections.
~ Billionaires are smarter, study says by Robert Frank.

PS. Unfortunately, the above quoted article did not reveal what part of the billionaires attended an elite school because their parents were billionaires who “gave the school large gifts” or top level politicians (“political connections“). The below Jonathan Wai’s  data provide a clue about it: