Meet the world's 50 richest billionaires in 2017

Bill Gates co-founded Microsoft with his friend Paul Allen, and served as CEO until 2000. He still sits on the company's board, but is no longer active in the day-to-day dealings.

Net worth: $89.4 billion

Age: 62

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Microsoft

After getting rejected from Harvard Business School, Warren Buffett went to Columbia instead where he studied under Benjamin Graham, who would become his mentor. He later bought Berkshire Hathaway in 1969 and transformed it into a powerhouse holding company.

Net worth: $81.7 billion

Age: 87

Citizenship: United States

Industry: Diversified

Source of wealth: Self-made; Berkshire Hathaway

Amancio Ortego controls fashion giant Inditex, which owns Zara, Massimo Dutti, Oysho, and others. At least part of his success can be attributed to Zara's fast-fashion business model.

Net worth: $75.9 billion

Age: 81

Citizenship: Spain

Industry: Retail

Source of wealth: Self-made; Inditex

Mark Zuckerberg launched TheFacebook.com when he was a sophomore in college before dropping out to work on the site full-time.

Net worth: $72.3 billion

Age: 33

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Facebook

Carlos Slim owns a large number of companies in Mexico through his conglomerate, Grupo Carso. He also controls America Movil, the largest operator of mobile phones in Latin America.

Net worth: $63.5 billion

Age: 77

Citizenship: Mexico

Industry: Diversified

Source of wealth: Self-made; Grupo Carso

Bernard Arnault is the chair of LVMH Moet Hennessy Louis Vuitton, which houses dozens of luxury brands. Arnault bought Christian Dior when he joined the business, and helped revive the company.

Net worth: $61.5 billion

Age: 68

Citizenship: France

Industry: Consumer

Source of wealth: Self-made/Inheritance; LVMH

Larry Ellison teamed up with two colleagues from an electronics company in 1977 to start their own programming firm, which then shortly landed a contract to build a relational database-management system for the CIA. The project later grew into what's known today as Oracle Corp., the second largest software maker behind Microsoft. He stepped down as CEO in 2014.

Net worth: $53.9 billion

Age: 73

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Oracle

Larry Page co-founded Google with Sergey Brin in 1998. He is now the CEO of Alphabet, which is the company that owns Google.

Net worth: $51.5 billion

Age: 44

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Google

Ingvar Kamprad founded IKEA, powerhouse furniture retailer, when he was 17. He moved IKEA and his family out of Sweden in the 1970s in order to avoid its taxes.

Net worth: $50.7 billion

Age: 91

Citizenship: Sweden

Industry: Retail

Source of wealth: Self-made; IKEA

Sergey Brin co-founded Google with Larry Page back in 1998. He is now the president of Alphabet, which is the company that owns Google.

Net worth: $50.2 billion

Age: 44

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Google

After being fired by Salomon Brothers, Bloomberg founded his eponymous financial-data firm in 1981. He added the news and media subsidiary in 1990, but the majority of Bloomberg LP's revenue continues to come from the sale of terminals. He later served as mayor of New York City for three terms.

Net worth: $48.9 billion (according to Forbes)

Age: 75

Citizenship: United States

Industry: Financial Services/Media

Source of wealth: Self-made; Bloomberg LP

Charles Koch runs Koch Industries as chairman and CEO with his brother, David. In addition to their conglomerate, the two brothers are major political influencers.

Net worth: $47.6 billion

Age: 82

Citizenship: United States

Industry: Industrial

Source of wealth: Self-made; Koch Industries

David Koch runs Koch Industries as executive vice president with his brother, Charles. Koch Industries manufactures, refines, and distributes a wide range of things, including chemicals, energy, minerals, and more.

Net worth: $47.6 billion

Age: 77

Citizenship: United States

Industry: Industrial

Source of wealth: Self-made; Koch Industries

Jack Ma started e-commerce company Alibaba with just $60,000 in 1999. Fifteen years later, it broke records with a $25 billion initial public offering.

Net worth: $46.6 billion

Age: 53

Citizenship: China

Industry: Technology

Source of wealth: Self-made; Alibaba

Samuel Robson "Rob" Walton is the oldest son of Walmart founders Helen and Sam Walton. He started working at the superstore empire back in 1969 and served as chairman from 1992 to 2015.

Net worth: $46.3 billion

Age: 73

Citizenship: United States

Industry: Retail

Source of wealth: Inherited; Walmart

James "Jim" Walton is the youngest son of Walmart founders Helen and Sam Walton. He co-manages Walton Enterprises, the holding company for the Walton family assets.

Net worth: $45.8 billion

Age: 69

Citizenship: United States

Industry: Retail

Source of wealth: Inherited; Walmart

Alice Walton is the youngest heir to Helen and Sam Walton's Walmart fortune. She hasn't taken an active role in running the superstore empire, but she co-manages Walton Enterprises, one of the family's two holding companies.

Net worth: $45.0 billion

Age: 68

Citizenship: United States

Industry: Retail

Source of wealth: Inherited; Walmart

Francoise Betterncourt Meyers is now the heiress to the L'Oreal cosmetics fortune after her mother's death in September 2017. She controls 33% of the company, according to Bloomberg.

Net worth: $44.3 billion

Age: 63

Citizenship: France

Industry: Consumer

Source of wealth: Inherited; L'Oreal Group

Ma Huateng, also known as Pony Ma, founded Tencent Holdings, which has a number of Internet and communication platforms in its portfolio, in 1998 when he was 26. Among others, its platforms include WeChat and QQ.

Net worth: $41.5 billion

Age: 46

Citizenship: China

Industry: Technology

Source of wealth: Self-made; Tencent Holdings

After his father died in 2002, Mukesh Ambani took over as chairman of Reliance Industries. He now controls about 40% of the company, which owns the world's largest oil refining complex.

Net worth: $40.9 billion

Age: 60

Citizenship: India

Industry: Energy

Source of wealth: Inherited/self-made; Reliance Industries

Hui chairs China Evergrande Group, a property developer that has worked on hundreds of projects across nearly 200 cities in China.

Net worth: $36.0 billion

Age: 58

Citizenship: China

Industry: Real Estate

Source of wealth: Self-made; China Evergrande Group

Sheldon Adelson and partners developed Computer Dealer's Exhibition (COMDEX), one of the largest trade shows in Las Vegas. He sold the company to Japan's Softbank for $860 million in 1995, and used the money to finance his purchase of the Sands Casino. He demolished that, and built the Venetian Casino Resort and the Sands Expo Convention Center in its place. In 2015, he bought Nevada's largest newspaper.

Net worth: $34.8 billion

Age: 84

Citizenship: United States

Industry: Entertainment/Real Estate

Source of wealth: Self-made; Las Vegas Sands

Steve Ballmer dropped out of business school at Stanford to become Microsoft's first business manager with a salary of $50,000 and a stake in the company. He eventually became CEO after Bill Gates stepped down and held the post until Satya Nadella replaced him in 2014.

Net worth: $33.9 billion

Age: 61

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Microsoft

Li Ka-shing dropped out of school at 16 to support his family by working in a factory making plastic flowers. He opened his own factory six years later — the predecessor to today's CK Hutchinson Holdings, which has interests in real estate, energy, and telecoms.

Net worth: $33.5 billion

Age: 89

Citizenship: Hong Kong

Industry: Real Estate

Source of wealth: Self-made; CK Hutchinson Holdings

Siblings John, Jacqueline, and the late-Forrest Mars inherited a stake in Mars, Inc. after their father died in 1999. The siblings are notoriously private, and don't actively manage the candy maker company. But they do run the Mars Foundation, which gives primarily to educational, environmental, cultural, and health-related causes.

Net worth: $33.5 billion each

Age: 82, 78

Citizenship: United States

Industry: Food and beverage

Source of wealth: Inherited; Mars Inc.

Jorge Lemann worked as a journalist and professional tennis player before jumping into finance in 1971. He co-founded 3G Capital in 2004, and has become known for his affinity for merges and acquisitions.

Net worth: $30.6 billion

Age: 78

Citizenship: Brazil

Industry: Food and beverage

Source of wealth: Self-made; 3G Capital

Wang Jianlin is the founder and chair of conglomerate Dalian Wanda Group, which has interests in a large number of companies, including property development, department stores, and entertainment.

Net worth: $28.4 billion

Age: 63

Citizenship: China

Industry: Real Estate

Source of wealth: Self-made; Dalian Wanda Group

Back in the 1960s, Phil Knight started a company that distributed Japanese sneakers in the US under the name Blue Ribbon Sports — which was the predecessor to Nike. He transformed a passion for running into a full blown sneaker and celebrity athletes empire.

Net worth: $26.6 billion

Age: 79

Citizenship: United States

Industry: Consumer

Source of wealth: Self-made; Nike

Francois Pinault founded luxury goods group Kering, which controls Gucci and Puma, among others.

Net worth: $25.1 billion

Age: 81

Citizenship: France

Industry: Consumer

Source of wealth: Self-made; Kering

Lee Shau Kee founded Henderson Land Development, which grew into a top real-estate developer in Hong Kong and China, in 1973.

Net worth: $24.6 billion

Age: 89

Citizenship: Hong Kong

Industry: Real Estate

Source of wealth: Self-made; Henderson Land Development

Dieter Schwarz joined his father's business in 1973 and soon opened the company's first discount supermarket. After his father died, he took over as CEO and expanded the business outside of Germany. The company operates Lidl, a grocery-store chain, and Kaufland, which is similar to Walmart.

Net worth: $24.0 billion

Age: 78

Citizenship: Germany

Industry: Retail

Source of wealth: Self-made; Schwarz Gruppe

Giovanni Ferroro controls Ferrero SpA, which makes Ferrero chocolates, Nutella, Kinder chocolates, and Tic Tacs.

Net worth: $23.8 billion

Age: 53

Citizenship: Italy

Industry: Food and beverage

Source of wealth: Inherited; Ferrero Group

Paul Allen, Microsoft co-founder, left the company before it went public. He remained a board member until 2000, and reduced his stake in the firm over time. He also founded Vulcan, his private investment vehicle.

Net worth: $23.6 billion

Age: 64

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Microsoft

After serving in the German military and working in corporate law stateside, Georg Schaeffler joined his father's company Schaeffler Group, which manufactures ball bearings for auto, aerospace, and industrial use. He is the chair and majority owner.

Net worth: $23.2 billion

Age: 53

Citizenship: Germany

Industry: Industrial

Source of wealth: Inherited/self-made; Schaeffler Group

Susanne Klatten inherited a stake in Bayerische Motoren Werke, which owns BMW and Rolls-Royce.

Net worth: $22.6 billion

Age: 55

Citizenship: Germany

Industry: Industrial

Source of wealth: Inherited; BMW

Serge Dassault is the CEO of Dassault Group, which has a controlling stake in military jet maker Dassault Aviation.

Net worth: $21.9 billion

Age: 92

Citizenship: France

Industry: Industrial

Source of wealth: Inherited; Dassault Group

Michael Dell started PC Ltd., the predecessor to Dell Inc., while he was a premed student in 1984. He dropped out of college to build computers full time, and the company went public by the time he was 23.

Net worth: $21.7 billion

Age: 52

Citizenship: United States

Industry: Technology

Source of wealth: Self-made; Dell

Lee Kun Hee is the chairman of Samsung Electronics, which is known for its consumer electronics division. He remains hospitalized after suffering a heart attack in 2014.

Net worth: $21.4 billion

Age: 75

Citizenship: Republic of Korea

Industry: Diversified

Source of wealth: Inherited; Samsung Electronics

Leonardo del Vecchio started Luxottica, the eyewear powerhouse, in 1961 in Milan. It owns Sunglass Hut, Ray-Ban, and Oakley, and manufacturers glasses for a large number of luxury brands.

Net worth: $21.1 billion

Age: 82

Citizenship: Italy

Industry: Consumer goods

Source of wealth: Self-made; Luxottica Group

Stefan Persson's father founded a women's clothing store, Hennes, in 1947, and later acquired a men's clothing store, Mauritz Widorss, in 1968 — creating Hennes & Mauritz. Or as it's known today, H&M.

Persson eventually joined his father after finishing school, and succeeded him as CEO later. Persson remains the chairman and largest shareholder, but in 2009, his son, Karl-Johan, took over the company.

Net worth: $21.0 billion

Age: 70

Citizenship: Sweden

Industry: Retail

Source of wealth: Inherited/self-made; H&M

Thomas Peterffy is the chair, CEO, and founder of Interactive Brokers Group, a huge electronic broker.

Net worth: $21.0 billion

Age: 73

Citizenship: United States

Industry: Finance

Source of wealth: Self-made; Interactive Brokers

Yang Huiyan controls Chinese real estate developer Country Garden Holdings. According to Bloomberg, her father co-founded the company in 1992 and then transferred his stake to her in 2005.

Net worth: $20.4 billion

Age: 36

Citizenship: China

Industry: Real Estate

Source of wealth: Inherited; Country Garden Holdings

Soviet-born American Len Blavatnik founded Access Industries in 1986. It began with only Russian investments, but now includes a diverse portfolio. He purchased a 20% stake in Tory Burch, now a retail powerhouse, in 2004, becoming the first and largest outside investor in the company.

Net worth: $20.0 billion

Age: 60

Citizenship: United States

Industry: Diversified

Source of wealth: Self-made; Access Industries

Stefan Quandt inherited a stake in Bayerische Motoren Werke, which owns BMW and Rolls-Royce.

Net worth: $20.0 billion

Age: 51

Citizenship: Germany

Industry: Industrial

Source of wealth: Inherited; BMW

Elon Musk is the CEO of Tesla, which makes electric cars. He's also the CEO of SpaceX and founded OpenAI and Neuralink.

Net worth: $19.9 billion

Age: 46

Citizenship: United States

Industry: Technology

Source of wealth: Self-made

Tadashi Yanai is the the founder and president of Fast Retailing, which owns retailer Uniqlo.

Net worth: $19.6 billion

Age: 68

Citizenship: Japan

Industry: Retail

Source of wealth: Self-made

Carl Icahn founded his own investment firm in 1968, and has invested in a number of high-profile companies over the years, including RJR Nabisco, Philips Petroleum, Viacom, Marvel, Time Warner, Netflix, Herbalife, and Apple.

Net worth: $19.2 billion

Age: 81

Citizenship: United States

Industry: Diversified

Source of wealth: Self-made; Icahn Enterprises

Ding Lei, also known as William Ding, is the founder and CEO of NetEase, which operates online games.

Net worth: $19.1 billion

Age: 45

Citizenship: China

Industry: Technology

Source of wealth: Self-made; NetEase