Steven A Ballmer

Microsoft chief attempted to take over Yahoo for $44.6 billion in February; attempt to compete with Google on search backfired after 6-month slugfest—featuring nasty Carl Icahn proxy fight—yielded no deal, sluggish stock price. Worse: Yahoo struck ad deal with Google soon after. Gaining some traction in online advertising; ranked first in display ads this June. Sales up 18% to $60 billion in 2007; net profits rose 26%. Entertainment division—videogame console Xbox, music player Zune—finally profitable. Detroit native dropped out of Stanford M.B.A. program to join former Harvard classmate Bill Gates in 1980. Gates' trusted advisor steadily climbed the ranks to become Microsoft's CEO in 2000. He retired from that role in 2014 with 333 million shares or a 4% stake, regulatory filings show. Bloomberg assumes that he's retained most of those shares, giving him a position valued at over $100 billion today, based on Microsoft's current stock price. He's likely also collected billions of dollars' worth of dividends over the years. Ballmer's fortune has grown by an estimated $29 billion this year to about $115 billion, ranking him fifth on the Bloomberg Billionaires Index.