NEW YORK—More than 30 billionaires, including Canadian-born Jeff Skoll, who made his fortune at eBay, pledged Wednesday to give away at least 50 per cent of their wealth to charity as part of a campaign by investor Warren Buffett and Microsoft founder Bill Gates.

Among the billionaires joining the campaign are New York Mayor Michael Bloomberg, entertainment executive Barry Diller, Oracle co-founder Larry Ellison, energy tycoon T. Boone Pickens, media mogul Ted Turner, David Rockefeller, and investor Ronald Perelman, according to The Giving Pledge website.