The latest Forbes 400 rich list shows the collective wealth of the richest 400 Americans has fallen by $US300 billion over the past year, as the economic downturn takes its toll on the wealthy.
Business magazine Forbes estimates that out of the 400 people on the list, 314 saw their wealth decline, the BBC reports.
The second richest person on the list - celebrated investor Warren Buffett - saw the biggest financial decline over the past year, losing an estimated $US10 billion.
Microsoft co-founder Bill Gates remains top of the list, worth an estimated $US50 billion.
Disgraced financier Sir Allen Stanford has fallen off the list.