As of 2015, the world's richest person is Bill Gates, who earned much of his 79.2 billion dollar fortune through Microsoft. He co-founded the company in 1975 and served as CEO from 1975 to 2008. Cascade Investment is a diversified investment company that accounts for the majority of Gates' current income. Gates also owns Corbis, a visual media licensing company.
The second-wealthiest person in the world, Carlos Slim Helú, made the majority of his $77.1 billion fortune in the telecommunications industry. He is the chairman and CEO of América Móvil, South America's largest mobile phone carrier. The third-wealthiest person in the world, Warren Buffett, made his fortune as an investor. Buffett is the owner and CEO of Berkshire Hathaway, a multinational company that owns businesses such as GEICO, Dairy Queen and Fruit of the Loom.
In 2009, Gates and Buffett began "The Giving Pledge," a campaign to convince the world's wealthiest people to give the majority of their wealth to philanthropic causes. So far, 137 billionaires have taken the pledge. Gates has given over $28 billion to philanthropic causes, and Buffett pledged to give away 99 percent of his wealth eventually. Helú has not joined the campaign but has given approximately $4 billion to charitable causes.