Rallying stocks and a strong euro swelled the list to the longest it has ever been.

Microsoft co-founder Bill Gates is No. 1 for the 10th straight year, but investor Warren Buffett is nipping at his heels. Gates' net worth is estimated at $46.6 billion, less than half the $100 billion it peaked at in 1998, but up about 13 percent from 2003.

Newcomers to the list included Rowling and Google founders Sergey Brin and Larry Page. All three debuted at No. 552 with $1 billion each. A number of billionaires share the same rank because Forbes reported their wealth as being the same.

Buffett wins the bragging rights for reaping the best gains of the year. He increased his net worth by $12.4 billion to $42.9 billion, significantly narrowing the gap between him and Gates.

German supermarket magnate Karl Albrecht remained in third place, with a fortune of $23 billion. Close behind were Saudi Arabia's Prince Alwaleed Bin Talal Alsaud, whose $21.5 billion nest egg put him just ahead of Microsoft's other co-founder, Paul Allen, fifth with $21 billion.

Rounding out the top 10 were Helen Walton, widow of Wal-Mart founder Sam Walton, and four members of her family. They were each worth an estimated $20 billion.

The magazine counted about 587 billionaires worldwide, up from 476 in 2003. Their total net worth was put at $1.9 trillion, up from $1.4 trillion in 2003.

"After two years of significantly falling fortunes, we really saw an uptick for just about everybody on the list," said Luisa Kroll, an associate editor at Forbes.

The strength of the euro in comparison to the dollar helped put 22 new billionaires on the list, for a total of 164 Europeans. Rising oil prices helped Russia add eight new billionaires for a total of 25. That puts the country in third place, behind the United States and Germany.

In the United States, billionaires probably gained last year not only from a 20 percent rise in stock prices, but also from reductions in taxes on dividends, capital gains and estate taxes, according to Mark Zandi, chief economist at Economy.com.