Of the 50 richest people in the world, most built their wealth up from nothing, creating some of the best companies out there — including Amazon, Berkshire Hathaway, Nike, and Google — along the way.

The 25 richest self-made billionaires on earth have accrued more than $850 billion combined, each with a personal net worth of at least $18 billion.

This comes from new data provided by Wealth-X, which conducts research on the super-wealthy, as featured in our recent list of the richest people on earth. Wealth-X maintains a database of dossiers on more than 110,000 ultra-high-net-worth people, using a proprietary valuation model to discern the size of their fortunes.

The list ranges from tech moguls like Bill Gates and Jeff Bezos to influential investors like Warren Buffett and Carl Icahn. Read on to learn how each of these 25 self-made billionaires earned their fortune.

25. Paul Allen


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Net worth: $18.3 billion

Age: 62

Country: US

Industry: Diversified investments

Source of wealth: Self-made; Microsoft

Alongside his cofounder Bill Gates, Paul Allen credits Microsoft for his fortune. Although Allen left the company before it went public in 1986, he remained a board member until 2000 and today holds a less than 5% stake. The college dropout went on to found Vulcan, his private-investment vehicle, shortly after leaving the software giant.

With lifetime donations exceeding $2 billion, Allen’s philanthropic efforts make him one of the most generous people in the world. The Paul G. Allen Family Foundation gives to global health causes, including $5 million to Seattle BioMed, $4 million to Global FinPrint — a conservation project focused on the preservation of sharks worldwide — and $7 million in grants to Alzheimer’s research. During West Africa’s Ebola pandemic in 2014, Allen gave more than $100 million to develop solutions to stem the outbreak. In October 2015, the foundation announced seven new grants totaling $11 million to prevent future widespread Ebola outbreaks.

The self-made billionaire also counts an extravagant lineup of cars, World War II fighter jets, real estate, and two sports teams — the Seattle Seahawks and the Portland Trailblazers — among his luxurious array of assets.