The 25 richest self-made billionaires

There are two types of billionaires: those who inherited their wealth, and those who built it from nothing. Our friends at Wealth-X, a database of information about ultra-high net worth individuals, focused on the latter to compile a list of the wealthiest self-made billionaires in the world. From tech mogul Bill Gates to Alibaba founder Jack Ma, here's who made the list.  25. Len Blavatnik Estimated net worth: $20.1 billion Though he's known as one of Britain's richest residents, Blavatnik is ...