Boston: chief executive officer Jeff Bezos saw his fortune rise by $2.72 billion (Dh9.98 billion) on Friday to $21.2 billion, highlighting a week in which the world's 40 richest people added $5.4 billion to their collective wealth.

Bezos' big day came as Amazon surged 16 per cent to close at $226.85 in New York. Strong demand for the Kindle tablet helped the Seattle-based company beat analysts' estimates in its latest earnings report.

Along with Bezos, the 24th-richest person on the planet, 25 other billionaires saw their net worth rise last week amid a rally in global stocks, according to the Bloomberg Billionaires Index. The assets of the 40 richest individuals now stand at $1.06 trillion.

"Most of these billionaires got super-wealthy because they had one big position, one big activity they were a majority owner of, that did amazingly well," said Brian Barish, president and chief investment officer of Cambiar Investors, a Denver-based institutional equities manager with $8 billion under management. "They are not just portfolio investors, they have an influence on the outcome of things as far as their stock is concerned."

Several billionaires with retail-derived fortunes saw their net worth slip.

Retail investors take hit

Four heirs of Wal-Mart Stores founder Sam Walton lost a combined $4.8 billion as reports of bribe allegations at Wal-Mart de Mexico lopped 5.5 per cent off its American counterpart and majority owner. Walton children Jim C. Walton, Samuel Robson Walton and Alice L. Walton, along with Christy R. Walton, the widow of Walton's second son, are collectively worth $93.6 billion.

Stefan Persson, the 64-year-old Swedish retailing titan, lost $671 million as Hennes and Mauritz (H&M) slipped because of increasingly negative analyst outlooks after the company missed earnings estimates last month. Of 34 analyst recommendations compiled by Bloomberg, 12 are sells, including last week's underperform rating issued by Sanford C. Bernstein.

Persson owns 38 per cent of H&M, Europe's second-biggest clothing retailer, and is ranked 16th with a net worth of $23.3 billion.

Slim's lead grows

Carlos Slim remains the richest person in the world as global stock markets added $3.7 billion to his net worth, which stands at $73 billion. Slim, 72, controls the largest mobile- phone company in the Americas, America Movil.

Strength in its Brazilian business boosted profit 38 per cent in the first quarter, the company said. The results sent shares up 2.2 per cent Friday to 16.98 pesos in Mexican trading.

The world's second-richest man and the wealthiest American, Bill Gates, saw his fortune gain $503 million even as Microsoft shares slipped 1.4 per cent to $31.98 in New York.

The majority of Gates' $63.8 billion fortune is held outside the company he co-founded. His portfolio benefited from strength in various smaller holdings, including a $2.3 billion equity stake in Fomento Economico Mexicano, a Latin American Coca-Cola bottler.

Other significant movers include Azim Hasham Premji, 66, who lost $837 million as shares of Wipro, India's third-largest software exporter, tumbled after its latest quarterly sales projection fell below analyst estimates. Premji's net worth is $16.4 billion, placing him 38th in the rankings.

Google gains

Google co-founders Larry Page, 39, and Sergey Brin, 38, both gained almost $500 million as investors bid up the company's stock on news of new product offerings.

They are worth $19.1 billion and $18.9 billion, respectively, putting them at 29th and 32nd.

Carl Icahn, the 76-year-old investor, rounds out the list at number 40 with a net worth of $15.7 billion.

The Bloomberg Billionaires Index takes measure of the world's wealthiest people based on market and economic changes and Bloomberg News reporting. Each net worth figure is updated every business day at 5:30 pm in New York and listed in US dollars.

Subscribers to the Bloomberg Professional services have access to billionaire profile pages that provide a transparent analysis of how each person's fortune was calculated.