In Pictures: Youngest Billionaires

Caption: John Arnold, U.S.
Age 34
$1.5 billion, self-made
Raised by a lawyer dad and accountant mom, Arnold whizzed through Vanderbilt University in three years. He became an oil trader for Enron, supposedly earning $750 million for the company in 2001, when he was just 27. He went into business for himself after Enron collapsed a year later. Today he runs hedge fund Centaurus Energy.