As of June 2015, the three richest men in the world are Bill Gates, Carlos Slim Helu and Warren Buffet, with each of these three individuals owning personal wealth exceeding $70 billion. Some other very wealthy individuals include Amancio Ortega, Larry Ellison, and Charles and David Koch.
Bill Gates co-founded Microsoft shortly after dropping out of Harvard University. It is now the world's largest software corporation, and his large equity interest in the company is the primary source of his wealth. He has funded numerous philanthropic initiatives in his role as co-chair of the Bill & Melinda Gates Foundation, including the successful eradication of polio in India. Gates has made personal charitable contributions totaling $29.5 billion over his lifetime.
Bill Gates has been the world's wealthiest man for much of his life, though others have surpassed his wealth from time to time. His closest contender is Carlos Slim Helu, a telecommunications magnate from Mexico who held the spot of world's wealthiest man for four years before it was reclaimed by Bill Gates in March 2014.
As of June 2015, Warren Buffet is the third richest man, with investment firm Berkshire Hathaway serving as the primary source of his wealth. Buffet pledged in 2006 to contribute most of his wealth to the Gates Foundation. In 2010 Buffet and Gates together launched The Giving Pledge, an initiative to promote philanthropic giving by billionaires.