Bill Gates's ex-assistant is now world's 5th-richest person. Microsoft co-founder is at 4

Microsoft co-founder Bill Gates's former assistant has shot up the list of the world's richest people and is currently ranked at number 5 on the Bloomberg Billionaires Index. Steve Ballmer may soon overtake his former boss who currently is ranked at number 4 on the list, Business Insider reported.

With an estimated fortune of $115 billion, Ballmer is currently richer than Larry Ellison ($114 billion), Warren Buffett ($111 billion), and Mark Zuckerberg ($108 billion), the index shows. Meanwhile, Bill Gates's fortune stands at $121 billion.

Ballmer's fortune is the result of an agreement he negotiated when he joined Microsoft in 1980 as assistant to the president after dropping out of Standford University. Despite his designation, he served as more of a business manager. As per a report in Forbes, Steve Ballmer originally negotiated a $50,000 base salary plus 10 percent of the profit growth he generated, but when his share grew exponentially, he agreed to swap it for a significant equity stake.

Eventually, he climbed through the ranks to become the CEO of the company from 2000 to 2014. He retired with 333 million shares or a 4 percent stake which Bloomberg believes he retained (at least most of them) giving him a position valued at over $100 billion today. Business Insider also noted that Ballmer is likely to have earned billions in dividends over the years.