Bill Gates has topped the Forbes list of the 400 richest Americans for the 13th year running.
For the first time since the lists began, only those with US$1 billion or more made it into the top 400.
"A nine-figure fortune won't get you much mention these days, at least not here," said the Forbes Rich List report. "This year, for the first time, everyone in the Forbes 400 has at least US$1 billion."
The collective net worth of America's richest citizens rose by US$120 billion to US$1.25 trillion, thanks to a surge in real estate, oil and other asset prices. However, five of the top 10 richest Americans still had links to technology.
Microsoft co-founder Bill Gates (US$53 billion) was followed in third place by Comdex founder Sheldon Adelson ($20.5bn). Oracle co-founder Larry Ellison (US$19.5 billion) came fourth, Microsoft's Paul Allen (US$16 billion) came fifth and Dell founder Michael Dell (US$15.5 billion) came ninth.
Adelson, currently a casino mogul, was again the biggest gainer with profits of US$1 million an hour since the 2004 Forbes 400 list was published.
Netscape pioneer James Clark rejoined the list after ploughing his profits from the technology industry into real estate and construction.
Making the list for the first time were Marvell Technology Group's husband-and-wife computer chip team of Weili Dai and Sehat Sutardja with US$1 billion each.
The Top Ten Forbes list of the 400 richest Americans:
1. William H. Gates III (US$53 billion)
2. Warren E. Buffett (US$46 billion)
3. Sheldon Adelson (US$20.5 billion)
4. Lawrence J. Ellison (US$19.5 billion)
5. Paul G. Allen (US$16 billion)
6. Jim C Walton (US$15.7 billion)
7. Christy Walton (US$15.6 billion)
8. S. Robson Walton ($15.6 billion)
9. Michael Dell (US$15.5 billion)
10. Alice L. Walton (US$15.5 billion)
Gates heads Forbes billionaire rich list
By Matt Chapman on Sep 25, 2006 9:57AM