Net worth: $27 billion

Age: 60

Country: US

Industry: Tech

Source of wealth: Self-made; Microsoft

Steve Ballmer dropped out of business school at Stanford in 1980 to join Harvard friend Bill Gates at Microsoft as the company's first business manager, earning a $50,000 salary and a stake in the company. During his tenure, Ballmer held positions as vice president of marketing, vice president of systems software, and executive vice president of sales and support, and was often referred to as "the numbers guy."

He became CEO of the company in 2000 after Gates stepped down, and he remained in charge of the software giant until Satya Nadella replaced him in 2014. While running Microsoft, the company's revenue grew by 294% and profits by 181% — although its market share was surpassed by Google and Apple during the same period. Still, the early stake Ballmer acquired in the company made him immensely wealthy. 

After stepping down as CEO, Ballmer fulfilled his dream of owning an NBA franchise, paying $2 billion in a deal to buy the Los Angeles Clippers, now his main venture. 

Ballmer's net worth has increased $4.8 billion in the last year.