1. Bill Gates
Net worth: $85.2 billion
Source of wealth: Self-made; Microsoft
At just 20, Bill Gates cofounded Microsoft with his childhood friend Paul Allen. Months before his 31st birthday, the company went public, making Gates a billionaire. He served as CEO of the software titan until 2000 and was its chairman and largest shareholder until 2014. Though he still sits on the company's board, Gates is no longer actively involved in Microsoft.
Gates is not only the richest man in the world — his net worth increased by $10.6 billion in the last year alone — but he's also the most generous. Since 1999, Gates and his wife have helmed the Bill & Melinda Gates Foundation, one of the most powerful charities in the world. The foundation — which controls an endowment of more than $40 billion — aims to lift millions of people out of poverty, with a heavy focus on eliminating HIV, malaria, and other infectious diseases. The couple is also working on a plan to bring mobile banking to the 2 billion adults who don't have a bank account.
He's also cofounder of the Giving Pledge, which he launched in 2010 with good friend and fellow billionaire Warren Buffett as a promise to donate 50% or more of their fortunes. The Giving Pledge now counts Mark Zuckerberg and Elon Musk among its 156 members.
2. Warren Buffett
Net worth: $77.2 billion
Industry: Diversified investments
Source of wealth: Self-made; Berkshire Hathaway
Berkshire Hathaway CEO Warren Buffett started his prodigious investing career at a young age. As a child he delivered newspapers on his bike, and by 11 the precocious Nebraska native had purchased his first shares in the stock market — Cities Service Preferred at $38 apiece — and sold them for a $5 profit. He was rejected from Harvard Business School, so Buffett went to Columbia Business School instead and learned under iconic value investor Benjamin Graham, who would become a mentor to the budding financier. Buffett worked as a securities analyst in the early-1950s before starting his own investment firm. He bought textile company Berkshire Hathaway in 1969, transforming it into a holding company that would house the many lucrative investments that helped build his massive fortune and earn the nickname "The Oracle of Omaha."
The array of portfolio companies and investments that made him rich may appear random — he's bet on companies including Coca-Cola, American Express, Geico, Fruit of the Loom, Dairy Queen, and General Motors — but they're all cash-generating machines that offer long-term value. In the past year, his net worth has increased by $13.1 billion.
A frugal man with a fondness for junk food, perhaps the most impressive part of Buffett's $60 billion fortune is that it doesn't include the more than $25 billion he's already given away. He's good friends with Microsoft cofounder Bill Gates, whom he collaborated with to create the Giving Pledge, a promise for billionaires to give away at least half of their wealth to charity.
3. Jeff Bezos
Net worth: $73.1 billion
Source of wealth: Self-made; Amazon.com
Jeff Bezos earned his massive fortune by introducing e-commerce to the world. After spending time in finance on Wall Street, Bezos founded Amazon.com in the garage of his Seattle home in 1994 and operated it exclusively as an online book retailer. The company went public three years later and has since grown to include everything from furniture to food to Amazon's own consumer-electronics products, generating $136 billion in revenue in 2016.
Bezos also has interests outside of Amazon, including investments in his privately owned space company Blue Origin, which successfully launchedits first spacecraft in 2015, and The Washington Post, the newspaper he bought in 2013.
Bezos' wealth has increased by $21.9 billion in the last year.
4. Mark Zuckerberg
Net worth: $58.5 billion
Source of wealth: Self-made; Facebook
In 2004, Mark Zuckerberg, then a 19-year-old sophomore at Harvard, launched TheFacebook.com, a rudimentary version of the now ubiquitous social network known as Facebook. Zuckerberg dropped out of college to work full-time as Facebook's CEO, and the site quickly exploded in popularity. Today, it attracts more than a billion users daily and is worth nearly $400 billion. At 32, Zuckerberg is by far the youngest of the 50 richest people in the world. His wealth has increased by $11.1 billion in the past year.
In December 2015, Zuckerberg and his wife, Priscilla Chan pledged give away 99% of their wealth in their lifetimes through an organization called the Chan Zuckerberg Initiative, though some critics noted the organization wasn't a nonprofit charity itself and found the announcement misleading.
But this isn't the couple's first foray into philanthropy. They donated $25 million in the fight against Ebola in 2015, and they gave $100 million worth of Facebook shares toward improving a New Jersey public-school system.
5. TIE: Charles Koch
Net worth: $47.9 billion
Industry: Diversified investments
Source of wealth: Inheritance/self-made; Koch Industries
Charles Koch is chairman and CEO of multifaceted conglomerate Koch Industries, the second-largest private company in America. His younger brother David is the executive vice president. The company employs 100,000 people and generates $100 billion in sales from its diverse holdings, which make everything from petrochemicals and Dixie Cups to raw clothing materials.
Outspoken in the world of conservative politics, the Koch brothers, who have a combined net worth of $95.8 billion, routinely fund political campaigns, although they took a step back during the 2016 election cycle.
However, in "Dark Money: The Hidden History of the Billionaires Behind the Rise of the Radical Right," it was revealed that Charles Koch's plans to reshape American politics date back 40 years, when he began strategizing and developing a libertarian movement.
According to businessinsider.com