Bill Gates: $78.2 billion
Bill Gates, the founder and chairman of Microsoft, was the year's biggest gainer. Gates recaptured the title of world's richest person on May 16 from Mexican investor Carlos Slim. Most of his assets are held in Cascade Investment, an entity through which he owns stakes in about three dozen publicly traded companies and several closely held businesses, including Four Seasons Hotels and Resorts and Corbis, a photo archive company.
