15 mega-billionaires who made a fortune last year

Bill Gates is once again the richest man in the world, adding another $10.6 billion to his net worth in the past year. Not a bad haul, but four other billionaires actually outearned Gates in the past year.

Using data from the Bloomberg Billionaires Index, which recently relaunched and expanded online to include 500 billionaires across the globe, Business Insider ranked which of the 30 richest billionaires in the world gained the most wealth in the past year.

Bloomberg's ranking updates daily to provide up-to-the-minute data on the world's wealthiest men and women, but for this ranking, wealth figures were used for the period starting February 28, 2016 and ending March 1, 2017. You can read about the billionaire index's full methodology here.

The two biggest gainers in the past year were Wang Wei, who added $22.7 billion to his fortune as the founder and majority owner of China's largest package delivery company, and Amazon.com CEO Jeff Bezos, who boosted his fortune by $21.9 billion thanks to Amazon's strong performance.

From tech moguls to skilled investors to retail giants, read on for the 15 billionaires whose wealth grew the most in the past year.

Note that Bloomberg does not report the net worth of its founder and owner Michael Bloomberg, who does not appear on this ranking, though other sources peg his fortune at roughly $45 billion.