The richest person in their 20s, 30s, 40s, and up

Net worth: $47.2 billion

Age: 31

Industry: Tech

At just 31, Facebook founder and CEO Mark Zuckerberg is already one of the richest people in the world with a net worth of $47.2 billion. Facebook continues to thrive, attracting more than a billion users daily in September — a 17% increase in traffic from the previous year. The company stock hit all-time highs in November after reporting $4.5 billion in quarterly earnings.

Zuckerberg has made some high-profile purchases of late. He reportedly spent $22 million on a new 3,200-square-foot home in New York City's West Village this year, and in 2014 he spent $100 million for 750 acres of secluded land on the North Shore of Kauai.

Zuck and his wife, Priscilla, are also incredibly generous with their wealth. The social media mogul has signed The Giving Pledge, promising to donate at least half of his wealth to charitable causes within his lifetime. The couple donated $25 million in the fight against Ebola last year, and gave $100 million worth of Facebook shares towards improving a New Jersey public-school system.

Source: Wealth-X

Net worth: $41.7 billion

Age: 42

Industry: Tech

Larry Page became a billionaire when Google went public in 2004 with a valuation of about $23 billion; 11 years later, the company is worth more than $500 billion.

Page and cofounder Sergey Brin — exceedingly wealthy in his own right with a net worth of $38 billion — have been shaking their company up lately. In August, Google announced that it would be forming a new parent company, Alphabet, to allow its different businesses to operate independently and move faster. Page and Brin still control the overarching entity as CEO and president, respectively.

Page doesn't make a lot of splashy purchases, but the alternative-energy advocate does own an eco-friendly mansion in Palo Alto that utilizes geothermal energy and rainwater capture. He's also an avid kiteboarder.

Source: Wealth-X

Net worth: $60 billion

Age: 51

Industry: Tech

After two straight quarters of impressive earnings in 2015, Amazon shares have shot up, and so has has the net worth of founder and CEO Jeff Bezos. He became the third-richest person in the US in October and now owns a fortune of at least $60 billion, trailing only Bill Gates and Warren Buffett.

Amazon is on fire, raking in profits of $92 million and $79 million in the second and third quarters this year; its stock is up more than 100% year-to-date. The company is dominating the competition in cloud computing through Amazon Web Services, which is used by major organizations including Comcast, Capital One, and the CIA.

Outside of Amazon, Bezos also has his hand in a few personal projects, including Blue Origin, his private space company, which announced its first successful rocket launch in September.

Source: Wealth-X

Net worth: $87.3 billion

Age: 60

Industry: Tech

Microsoft founder Bill Gates started programming computers when he was only 13 years old, and he cofounded his iconic software company with childhood friend Paul Allen in 1975 after dropping out of Harvard. The company minted Gates a fortune that now exceeds $87 billion.

But in recent years Gates has shifted his focus away from Microsoft, where he's still an advisor, and toward the Bill and Melinda Gates Foundation. He and his wife founded the charity in 2000 after reading an article about curable diseases causing millions of child deaths in developing countries. Since then, the organization has given away $34.5 billion to an array of causes, including efforts to eliminate HIV, malaria and many other infectious diseases. They also support agricultural development, emergency relief, global libraries, urban poverty, and education.

Along with many of his fellow billionaires, Gates has pledged to give away at least half of his wealth to charity after his death through The Giving Pledge, which he and Berkshire Hathaway CEO Warren Buffett created together.

Source: Wealth-X

Net worth: $73.2 billion

Age: 79

Industry: Retail

With a net worth of at least $73.2 billion, Amancio Ortega is the second-richest man in the world, thanks primarily to his control of the Spanish fashion behemoth Inditex. He keeps a low profile and dresses modestly, but he still puts his fortune to use: He owns the Torre Picasso, the tallest skyscraper in Spain, as well as The Epic Residences and Hotel in Miami. Like a true billionaire, Ortega also owns a private jet worth $45 million.

His rising wealth this past year is directly tied to Inditex's rapid growth. The company reported a sharp rise in sales and profits and nearly 100 new stores in September, hitting a $100 billion valuation. The company now has nearly 6,800 stores worldwide. The secret to this success is the fast-fashion giant Zara, the company's biggest brand. The chain is changing the landscape of retail as its chic yet affordable designs continue to appeal to demanding customers who constantly crave new styles at low prices.

Source: Wealth-X

Net worth: $62.4 billion

Age: 85

Industry: Finance

Berkshire Hathaway CEO Warren Buffett bought his first stock at age 11 and never looked back. Since then, Buffett has continued to amass a fortune of more than $62 billion through a near-clairvoyant knack for making smart, long-term bets on companies like Coca-Cola and American Express. His company has grown exponentially since he took over in 1964: $1,000 invested in Berkshire Hathaway stock then would be worth more than $10 million today.

He may be the second-richest person in the US, but Buffett doesn't like to show off his enormous wealth. He drives his own car and still lives in the same house he bought in Omaha, Nebraska, in 1958.

Buffett is a friend of Microsoft cofounder Bill Gates, whom he collaborated with on the Giving Pledge, a promise for billionaires to give away at least 50% of their wealth to charity. Buffett has given away nearly $3 billion in each of the past two years, and $21.5 billion in his lifetime.

Source: Wealth-X

Net worth: $31.4 billion

Age: 93

Industry: Retail

The heiress to the L’Oreal cosmetics fortune and the company’s largest shareholder, Liliane Bettencourt is worth more than $31 billion. She no longer has a hand in business operations, but both L’Oreal and the Bettencourt Schueller Foundation she cofounded with her late husband continue to prosper. She's an avid art collector, owning pieces by Picasso, Matisse, and Munch.

Bettencourt’s known for more than just her immense wealth though. She's made French headlines in recent years as the central figure in an infamous trial that closed in 2015, in which judges examined whether the billionaire was taken advantage of by those close to her. In May, eight people were convicted of exploiting Bettencourt.

Source: Wealth-X