The richest people in the world have gotten poorer, just like the rest of us. This year the world's billionaires have an average net worth of $3 billion, down 23% in 12 months. The world now has 793 billionaires, down from 1,125 a year ago. After slipping in recent years, the U.S. is regaining its dominance as a repository of wealth. Americans account for 44% of the money and 45% of the list's slo