IN A country where half the people live in poverty, one man made $3.5 billion (¤2.57 billion) last month. And it wasn’t a one-off deal.

The Mexican billionaire Carlos Slim has been adding to his fortune at that rate all year. So rapidly has Slim’s fortune swelled that he has overtaken Microsoft co-founder Bill Gates to become the world’s richest man. As Gates has found, it’s a title that bestows a whole new level of scrutiny as well as responsibility on its owner.

The sixth and youngest child of a Lebanese immigrant and shopkeeper, the portly, cigar-smoking Slim and his children dominate business in Mexico.

The 67-year-old’s main companies, Telmex and America Movil, tower over the telecoms market in Mexico and have sold mobile phones to 130m people throughout the Americas. Slim’s rich pickings stretch across a whole range of businesses and include Mexico’s largest offshore oil platform as well as retail, banking, insurance, mining, road building, CDs and cigarettes.

Slim’s big break began in 1990, after the government sold the phone monopoly Telefonos de Mexico to a group that he led.

By 2005, Slim was the fifth-richest man in the world, according to Forbes magazine. Last year, Forbes moved him up to No 3 and this year he reached second place, with an estimated net worth of $53.1 billion.

Now, Sentido Comun, a Mexican publication that tracks Slim’s fortune closely, is reporting that the value of his companies has grown so fast this year that he has bumped Gates from first place.

America Movil’s share price is up 39% so far this year. His fixed-line telephone company, Telefonos de Mexico, which has a 90% market share in Mexico, is up 34%. These rises have given Slim an estimated fortune of $67.8 billion, a figure that soars above Forbes’s $56 billion estimate for Gates.

It’s a lot of money anywhere, but especially in Mexico, where 17.6% of the general population and more than a quarter of the rural population live in extreme poverty.

Against this background, Slim makes a large target and his new-found position at the top of the pile only adds to his problems. Like Gates, Slim has been accused of being a monopolist, and Mexico’s president, Felipe Calderon, who took office last December, is under pressure to show that he is prepared to tackle Mexico’s powerful monopolies and duopolies.

Calderon came to power supported by big business, but, in a recent interview with Time magazine, the president said he wanted to “reduce the power” of monopolies and create “more competitive market conditions”. He was elected by a small majority and the power of local monopolies, which control everything from telecoms to beer, remains a hot issue with voters.

So far, Slim’s army of lawyers has successfully fought off plans to declare Telmex a “dominant” player, which would allow regulators greater scrutiny of the company.

Like any number of rich men before him, Slim has turned to philanthropy.

In recent weeks, Telmex Foundation, Latin America’s largest corporate giver, has been publishing daily colour full-page ads in leading Mexican newspapers to publicise its many charitable schemes.

Among other activities Telmex Foundation provides bicycles to rural children so they can get to school and free medical care for the poor. Slim has also doubled the size of his family charity, the Carso Foundation, to $2.5 billion.

Slim’s wealth may have eclipsed Gates’s, but so far his charitable deeds pale in comparison. The Bill and Melinda Gates Foundation is the largest charitable body in America with an endowment of $24 billion.

Gates’s reign as the world’s richest man may be over, but it seems we have merely swapped one philanthropic monopolist for another.

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