Forbes has posted their annual list of the twenty richest people in the world. Number one is not Bill Gates, nor is it Warren Buffet. Mexican telecom tycoon Carlos Slim Helu edged out Gates with a net worth of $53.5 billion, which is $18 billion more than he had a year ago. U.S. billionaires still dominate the ranks–but they are losing their grip . Americans account for 40% of the world’s billionaires, down from 45% a year ago. Bill Gates was the world’s richest person fourteen of the past fifteen years.