Slim, 70, took the top spot for the first time in the list published on Wednesday, pushing the Microsoft founder out as he rose from third place on the success of America Movil, Latin America´s biggest mobile phone operator.[break]
His fortune was estimated at 53.5 billion dollars, according to the new Forbes ranking out Wednesday.
"These numbers come from the price of the stock of the companies so we´re happy that investors are confident about Mexico, confident about Latin America and confident about our companies," Arturo Elias Ayub, spokesman for Slim´s Telmex group, told AFP.
Slim´s fortune rose 18.5 billion in 12 months, and shares of America Movil, of which he owns a 23-billion-dollar stake, were up 35 percent in a year, according to Forbes.
Slim learned his business acumen at an early age; his father, a Lebanese immigrant, gave each of his children a savings book for managing their income and expenses.
Slim studied civil engineering and later built up the telephone monopoly Telmex after acquiring it from the government in 1990.
The softly-spoken billionaire last month received authorization to merge three of his telecommunications companies to form a regional giant, with 250 million customers in 18 countries.
His business empire is ever-present across Mexico, including department stores, building companies and the Inbursa financial group.
Amid the financial crisis of 2008, he continued his trademark behavior of buying up struggling businesses, for which he first became famous during the Latin American economic crisis of the early 1980s.
"Instead of stopping investing, he invests more when a crisis comes and the results have always been good," Ayub said.
In 2008, Slim bought a minority stake in The New York Times as the stock sunk.
He has recently made investments in telecommunications across the Americas, and also in infrastructure, including water and electricity companies, Ayub said.
Slim, a widower with six children, has handed over the daily operations of his companies to his three sons and business partners and is a well-known public figure in Mexico.
His is also a baseball fanatic, and known for his philanthropy although not on the scale of Gates.
Through two foundations he has invested some 10 billion dollars in health, education, justice and sports projects in Mexico and Latin America.
World´s 20 richest people: Forbes
The top 10 richest people in the world have a combined worth of 342 billion dollars in 2010, up from 254 billion a year ago. Here are the 20 wealthiest, as announced Wednesday by Forbes magazine in its annual list of the world´s billionaires:
1. Carlos Slim Helu and family. Mexico. Telecoms. 53.5 billion dollars.
2. Bill Gates. US. Microsoft. 53 billion dollars.
3. Warren Buffett. US. Berkshire Hathaway. 47 billion dollars.
4. Mukesh Ambani. India. Oil, gas. 29 billion dollars.
5. Lakshmi Mittal. India. Steel. 28.7 billion dollars.
6. Lawrence Ellison. US. Oracle. 28 billion dollars.
7. Bernard Arnault. France. LVMH luxury goods. 27.5 billion dollars.
8. Eike Batista. Brazil. Mining, oil. 27 billion dollars.
9. Amancio Ortega. Spain. Clothing retail. 25 billion dollars.
10. Karl Albrecht. Germany. Supermarkets. 23.5 billion dollars.
11. Ingvar Kamprad and family. Sweden. Ikea. 23 billion dollars.
12. Christy Walton and family. US. Walmart. 22.5 billion dollars.
13. Stefan Persson. Sweden. Hennes and Mauritz. 22.4 billion dollars.
14. Li Ka-shing. Hong Kong. Diversified. 21 billion dollars.
15. Jim Walton. US. Walmart. 20.7 billion dollars.
16. Alice Walton. US. Walmart. 20.6 billion dollars.
17. Liliane Bettencourt. France. L´Oreal. 20 billion dollars.
18. S. Robson Walton. Walmart. 19.8 billion dollars.
19. Prince Alwaleed Bin Talal Alsaud. Saudi Arabia. Investments. 19.4 billion dollars.
20. David Thomson and family. Canada. Inheritance. 19 billion dollars.
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