Revealed: The world’s 10 richest CEOs

The world’s richest chief executives have all either founded or built companies from the ground up, in many cases transforming their industries. While some of them inherited wealth, most came from modest beginnings. One started as a newspaper boy, another as an insurance salesman, a third as a mortgage broker. Our list of the 10 richest CEOs spans across four generations; the youngest CEO on the list was born in 1984, the oldest in 1930. The ranking is based on net worth figures from Wealth-X, a research firm that provides information on ultra high net worth individuals to private banks and consulting firms. Each chief executive's net worth was calculated as of March 16, 2012 and consists of public and private holdings, estimated cash salaries, dividends, and all other investible assets. Their wealth is so large that it makes the earnings of the average CEO — with their stock options, pension plans and bonuses — look like pocket change. But the recession in 2008 and a slowdown in global growth in recent years have dented the wealth of some of them. So, who are the world’s billionaire-CEOs? Click ahead to find out

10. Aliko Dangote, 55

Company: Dangote Group

Net worth: $11.2 billion

Compensation: $16, 510

Billionaire Aliko Dangote is the richest man in Africa, according to Forbes. He is also the founder and CEO of Dangote Group, which owns Nigeria’s largest listed company by market cap — Dangote Cement. Dangote founded the group in 1977 as a rice, sugar and cement trading company before it grew into a full-scale manufacturing firm and one of Africa’s largest conglomerates. The group now has 13 subsidiaries in sectors like real estate, telecommunications and oil and gas. It operates in 14 African countries and recorded revenue of more than $3 billion in 2010, according to its website.

Known as Africa's "cement king," Dangote consolidated cement interests spread throughout the continent in 2010 under parent company, Dangote Cement, which was then listed on the Nigerian Stock Exchange. In February, Dangote Cement opened a $1 billion manufacturing plant in the southeastern Nigerian state of Ogun, boosting the country’s cement production capacity by more than 40 percent. Earlier this month, Dangote announced plans to list the company on the London Stock Exchange in 2013 and free-float a 20 percent stake in the firm to finance its rapid expansion.

The majority of Dangote’s wealth comes from his stake in Dangote Cement, which is estimated to be at least $9.6 billion, according to Wealth-X. His second biggest asset is his holding in Dangote Group, which is valued at over $450 million.

9. Mark Zuckerberg, 27

Company: Facebook

Net worth: $18.1 billion

2011 compensation: $1.49 million

At 27-years-old, Mark Zuckerberg is the youngest CEO on the list. As the founder and CEO of the world’s largest social networking website with 845 million monthly users, Zuckerberg is likely to leap up the rankings once Facebook goes public this year. His roughly 28 percent stake in the company is valued at $17.9 billion, according to Wealth-X. The tech giant’s highly-anticipated $5 billion IPO could value the company at $100 billion and push Zuckerberg’s net worth up to $28 billion.

Zuckerberg co-founded Facebook with friends in his Harvard University dorm in 2004 as a way to connect the university’s students. He dropped out of Harvard to expand the social networking site globally. Facebook’s growth has catapulted the company’s revenue to $3.71 billion in 2011 and its workforce has grown to 3,200. Worldwide, users spend about six hours a month on Facebook, and a recent survey revealed that long-time users are not tiring of posting personal details on the social media site.

Despite plans to take the company public this year, Zuckerberg will keep almost complete control over the social media enterprise. Its IPO prospectus states that Zuckerberg will “control all matters” submitted to stockholders for vote, along with the overall management and direction of the firm.

8. Larry Page, 39

Company: Google

Net worth: $18.3 billion

2010 compensation: $1,786

Google co-founder Larry Page was the company’s first CEO, but he stepped aside in 2001 and became President of products. Page returned to the post of Chief Executive last year.

Page, along with classmate Sergey Brin, founded the company in 1998 while pursuing a PhD at Stanford University. Considered a pioneer in the field, Page was born into a family of computer scientists with both parents’ professors at the University of Michigan — where he graduated from with a bachelor’s degree in engineering. The tech mogul has been quoted as saying that he began playing with computers as a six-year-old and knew by age 12 that he was going to start a company.

Page’s wealth skyrocketed in 2004 when Google went public on the Nasdaq Stock Market — raising $1.7 billion, making it thelargest IPO by a U.S. Internet firm to date. The estimated value of his shares in Google is $16.4 billion, according to Wealth-X. Page also owns a $45 million 194 foot long yacht named Senses. Other big assets include Page’s Palo Alto, California home, valued at $6 million.

Known for his philanthropy, Page is the trustee of the X-Prize Foundation, which offers cash prices for radical scientific breakthroughs that benefit people.

Since taking back the helm at Google last year, Page has made headlines for pulling the plug on several key projects

7. Lakshmi Mittal, 61

Company: Arcelor-Mittal

Net worth: $19.1 billion

2011 compensation: $1,739,000

Lakshmi Mittal is the founder and CEO of ArcelorMittal — the world’s largest steelmaker.

The 61-year old steel tycoon founded the company in 1976 as LNM Group, parting ways from his India-based family steel business, which he helped run to venture out on his own. The firm went on to merge with Arcelor in 2006 to form ArcelorMittal.

Mittal is also chairman of the group and his stake in the company is valued at $13.2 billion, according to Wealth-X. His other large assets include homes in London, U.K. valued at about $500 million, while his yacht named “Amevi” is worth $200 million. An avid soccer fan, Mittal also owns a 33 percent stake in English Premier League football club Queen’s Park Rangers.

Other family members involved in ArcelorMittal include his son and heir apparent Aditya (pictured), who is the CFO, while daughter Vanisha is one of 10 board members. Vanisha’s 2004 wedding to Amit Bhatia made headlines for its extravagance and is considered the third most expensive wedding in modern times, costing more than $55 million. The wedding took place at France’s Versailles Palace and the senior Mittal reportedly paid for 1,000 guests to stay one week at five-star hotels in Paris.

Euro zone woes and falling steel demand have hit Mittal and his company hard. The steelmaker made headlines last October when it backed out of a deal with U.S. coal giant Peabody.

6. Sheldon Adelson, 78

Company: Las Vegas Sands

Net worth: $24.6 billion

2010 compensation: $11,356,866

Sheldon Adelson is the chairman and CEO of Las Vegas Sands, the most valuable publicly traded U.S. casino company.

Adelson rose from poverty in Boston and worked his way into the financial industry before developing one of the world’s largest computer tradeshows — COMDEX in 1979. Ten years later, he bought the Sands Hotel & Casino in Las Vegas and constructed the Sands Expo and Convention Centre. In 1995, Adelson sold the COMDEX trade shows formore than $860 million and constructed the $1.5 billion Venetian Resort Hotel Casino.

Since then, he’s expanded his empire globally, and now owns the Sands Macao and the Venetian Macao in southeastern China — a region now known as the world’s biggest gaming centre. He also opened the Marina Bay Sands casino in Singapore.

Adelson’s stake in Las Vegas Sands is estimated to be worth $14.8 billion. Other notable assets include his home in Newton, Massachusetts, valued at $4.9 million.

Adelson and wife, Miriam, are also known as keen supporters of U.S. presidential candidate Newt Gingrich, donating nearly $11 million to a political committee that supports Gingrich's campaign in January. The casino mogul has also signaled that he would write big checks to Republican candidate Mitt Romney if he wins the nomination.

5. Charles G. Koch, 76

Company: Koch Industries

Net worth: $24.7 billion

Compensation: N/A

Charles G. Koch has been the chairman and CEO of Koch Industries — one of the largest privately owned companies in the U.S. — since 1967. The group’s annual revenue is more than $100 billion, according to Forbes.

Koch Industries was co-founded by Charles’s father Fred C. Koch and classmate Lewis E. Winkler in 1925 as Winkler-Koch Engineering. The company developed an innovative cracking method of turning crude oil into gasoline. After the death of Fred Koch in 1967, sons Charles and David Koch, both engineers, took control of the Kansas-based mid-size firm and expanded the Koch empire globally to have a presence in 60 countries with interests in energy, textiles, petrochemicals and pulp and paper. Koch Industries is considered among the world’s top independent oil traders by turnover.

Charles Koch’s stake in the group is estimated to be at least $22.4 billion, according to Wealth-X. Other big assets include his homes in Aspen, Colorado and Indian Wells, California, which are estimated to be worth $7 million and $5 million respectively.

4. Eike Batista, 56

Company: EBX

Net worth: $31.6 billion

Compensation: N/A

Eike Batista is South America’s richest man, and the founder and CEO of holding company EBX.

Known for taking risks in his rise from a door-to-door insurance salesman to Brazil’s leading business tycoon, Batista first made his fortune buying gold from Amazon miners in the early 1980s before going on to found EBX in 1983. The group now consists of more than 10 companies, five of which are listed on Brazil’s benchmark Bovespa exchange. The diversified conglomerates’ interests include oil, logistics, mining, real estate and sports.

Batista’s stake in oil subsidiary OGX, which is Brazil’s second largest oil company, is estimated to be worth $19.1 billion, according to Wealth-X. His shares in energy firm MPX are valued at $2.3 billion, while his stake in mining subsidiary MMX is believed to be worth $1.9 billion. He is also reported to have a $61 million Gulfstream jet.

The flamboyant billionaire is a former world powerboat-racing champion and has more than 700,000 Twitter followers. Already the richest person in Brazil, Batista has declared plans to be the richest person in the worldone day.

In March this year, Batista’s 20-year-old son Thor struck and killed a cyclist in Rio de Janeiro while driving his father’s $1.3 million Mercedes-Benz SLR McLaren. The incident sparked a debate about the rich-poor divide in the country

3. Lawrence J. Ellison, 67

Company: Oracle

Net worth: $35 billion

2011 compensation: $77.6 million

As the co-founder and CEO of Oracle, Larry Ellison is also the sixth richest person in the world and the third wealthiest in the U.S., according to Forbes.

Ellison co-founded Oracle under the name Software Development Laboratories (SDL) in 1977. The company picked up a contract with the CIA in the same year to build a database program code-named "Oracle." In 1980, the firm had only eight employees and turnover of less than $1 million, but after IBM adopted Oracle’s mainframe systems the following year, its sales doubled every year for the next seven. Since then, Oracle has grown to over 380,000 customers and is the third-largest software company based on revenues behind IBM and Microsoft.

Ellison’s stake in Oracle is estimated to be about $32.8 billion, according to Wealth-X. A sailing enthusiast, his yacht Rising Sun is one of the largest privately owned vessels in the world, worth an estimated $200 million. In 2009, Ellison also bought the Indian Wells ATP tennis championship event, the BNP Paribas Open, for $100 million. Other notable assets include his Japanese-style home in California valued at $70 million.

Ellison has consistently topped the list of the world’s highest paid CEOs in the past decade. In 2009, he was the highest paid CEO withcompensation totaling $84.5 million. Despite his growing wealth, Ellison is also known for his philanthropy.

2. Warren Buffett, 81

Company: Berkshire Hathaway

Net worth: $44.7 billion

2011 compensation: $491,925

As chairman and CEO of Berkshire Hathaway, Warren Buffett is the world’s second-richest CEO and the world’s third-richest man. His company’s holdings include American Express, Coca-Cola, Costco, and Moody’s.

Buffett’s early job as a paperboy in Omaha, Nebraska in the 1940s helped him earn the $5,000 and launched him into the world of value investing and eventually led to the creation of the Berkshire investment empire.

The estimated value of Buffett’s class-A shares in Berkshire Hathaway is about $42.6 billion, while his class-B shares are worth $2.1 billion, according to Wealth-X. Buffett’s Laguna Beach, California home is estimated to be worth $2.7 million but he’s renowned for living in the same house that he bought in Ohama in 1958.

Despite accumulating immense wealth, Buffettpledged in 2006 to gradually give away all of his company stock to philanthropic foundations. In all, he will give away more than 99 percent of his wealth.

Buffett called last August for the U.S government to “stop coddling” the super-richand increase their taxes. The move led U.S. President Barrack Obama to propose legislation of a minimum tax rate of 30 percenton those who earn $1 million or more a year, known as the “Buffett tax”.

1. Carlos Slim, 72

Companies: Grupo Carso, Telmex, America Movil

Net worth: $70 billion

Compensation: N/A Carlos

Slim has been the world’s richest man for the past three years, and his wealth is equivalent to nearly 6 percent of Mexico’s annual economic output.

Slim is the Chairman and CEO at three of his companies: telecom giants Telmex and America Movil, which is the world’s third largest cellphone company by subscribers, and conglomerate Grupo Carso. Mexico-born Slim, who is of Lebanese descent, studied engineering before starting his own company in 1965, which would later be known as Grupo Carso. Slim continued to build his empire by purchasing troubled companies and turning them around. He also has stakes in some well-known North American names like the New York Times, and retailer Saks.

The majority of Slim’s wealth comes from his stake in Grupo Carso, which is estimated to be worth $60.5 billion, according to Wealth-X. He is well-known for his art collection, which is valued at $700 million. Slim is believed to have the largest number of sculptures by Auguste Rodin outside of France, which is displayed in a newly built museum in Mexico City, named after his late wife Soumaya.

Despite his status as the world’s wealthiest man, Slim is known to live in a modest six-bedroom house in Mexico City and drives himself to work , with his bodyguards following closely.

Slim retained the title of the world’s richest man in 2012, but his net worth declined $5 billion