Forbes 2011 ranking of the top 10:

Here is the Forbes 2011 ranking of the top 10:

1. Carlos Slim (Mexico) – $74bn, telecommunications

Slim, 71, first showed business talent as a 10-year-old selling drinks and snacks to his family. After studying engineering, he founded a real estate company and worked as a trader on the Mexican stock exchange. A cigar-smoker, Slim is said to have a "Midas touch" for his ability to acquire struggling firms and turn them into cash-cows.

His enormous wealth contrasts starkly with his frugal lifestyle. He has lived in the same house for 40 years and drives an aging Mercedes Benz, although it is armored and trailed by bodyguards.

He is involved in combating poverty, illiteracy and poor healthcare in Latin America and promotes sports projects for the poor, but has never hinted at plans to donate large chunks of his wealth to charity.

2. Bill Gates (USA) – $56bn, Microsoft

Sensing the start of the personal computer revolution, Gates, 55, dropped out of Harvard University in 1975 to found Microsoft and pursue the vision of a computer in every home. Microsoft went public in 1986 and by the next year the soaring stock made Gates, at 31, the youngest self-made billionaire.

In 2008 he stepped down from from what is now the world's largest software firm to work on the Bill and Melinda Gates Foundation, to which he has given $28 billion of his personal fortune.

Together with his wife Melinda, and Warren Buffett, he has convinced 57 US billionaires to sign up to the Giving Pledge and publicly vow to give away at least 50% of their fortune during their life or upon their death.

3. Warren Buffett (USA) – $50bn, Berkshire Hathaway

The interests of the Nebraska-based conglomerate that Buffett, 80, has run since 1965 run from railroads to ice cream.

In 2006 he pledged to give away 99% of his wealth to the Bill and Melinda Gates Foundation and family charities over his life. So far he has given $8 billion.

4. Bernard Arnault (France) – $41bn, LVMH

Arnault, 62, a friend of French president Nicolas Sarkozy, was educated at the prestigious Ecole Polytechnique and joined his father's construction company at 25.

He earned the reputation of a ruthless corporate operator after he pushed out shareholder rivals in the early days of building the LVMH group in the 1990s with the Louis Vuitton, Moet and Hennessy brands. It is now the world's biggest luxury goods group. However, it was clear his image as a predator had stuck to him when he fought in vain to acquire Gucci in 1999 and 2000.

Just this week, however, he snapped up Roman jeweler Bulgari for $5.18bn.

5. Larry Ellison (USA) - $39.5bn, Oracle Corp

Ellison, the flamboyant Oracle founder and CEO, is considered one of the old guard of Silicon Valley, as well as for his public outbursts against rivals such as German software maker SAP AG. Late last year he attacked Hewlett Packard and its board for the abrupt and – he said – unfair sacking of his friend Mark Hurd, whom Ellison swiftly hired.

He also won the America's Cup yachting race last year, and is supposedly a model for the character Tony Stark in the Iron Man films.

6. Lakshmi Mittal (India) – $31.1bn, steel

London-based steel tycoon Mittal, 60, runs ArcelorMittal, the world's largest steel manufacturer.

His firm is largely funding a $29 million spiraling red edifice, designed by Turner prize-winning artist Anish Kapoor and taller than New York's Statue of Liberty, that will tower over London's Olympic Park for the 2012 games.

In 2005 he spent $10m to promote sporting talent and encourage potential Olympians in his homeland after being disappointed by India's lone medal at the Athens Games.

7. Amancio Ortega (Spain) – $31bn, retail

Amancio Ortega, 74, started his clothing business in the 1960s making dressing gowns in his garage in La Coruna. His company Inditex owns the Zara fashion house and is now the world's biggest clothing retailer. Ortega closely guards his privacy and does not give media interviews.

He announced in January that he plans to step down as chairman of the company.

8. Eike Batista (Brazil) – $30bn, mining, oil

A half-German college dropout who for years struggled to emerge from the shadow of his well-known father, Batista has long said he wants nothing less than to be Brazil's – and the world's – richest person.

Everything about the 53-year-old, from the Mercedes-Benz SLR McLaren sports car he keeps as decoration in his parlor to the "X" in the name of all his companies that represents wealth multiplication, speaks volumes about his unashamed ambition.

A speedboat racer who was married to a famous Rio de Janeiro Carnival queen, Batista dined with pop star Madonna in Rio last year and, according to local reports, handed her a check over dinner for $7m as a donation for her social projects.

He has a burning ambition to transform Rio into a modern, thriving city. Just before it was awarded the 2016 Olympic Games, he bought up a nearby marina that will be a hub of the games – an example of his eye for a well timed deal.

9. Mukesh Ambani (India) – $27bn, petrochemicals, oil and gas

A chemical engineer by training, Mukesh, 53, dropped out of an MBA from Stanford University and joined Reliance in 1981.

While he said in 2009 he would take a two-thirds pay cut after the Indian prime minister made comments on "vulgar salaries," he gave his wife a private jet on her birthday and splashed out $1 billion on a 27-story home. He has a volatile relationship with his younger brother Anil, and they have fought over interests from oil and gas, retail, telecoms, entertainment, financial services to infrastructure.

10. Christy Walton & family (USA) – $26.5bn , Wal-Mart

Christy Walton is the widow of John Walton, the son of Wal-Mart founder Sam Walton. Sam Walton built the global Wal-Mart empire from a single dime store in Arkansas into the world's largest retailer.