The latest Forbes list of the world's richest people shows there are now more than 1200 billionaires across the world.
The record figure of 1210 billionaires includes more than 100 billionaires each in both China and Russia. Previously only the United States had reached that level.
The world's richest man is still Mexican telecommunications tycoon Carlos Slim, who is worth $US74 billion.
The US has Microsoft's Bill Gates, worth $US56 billion, and investor Warren Buffett, worth $50 billion, plus six billionaires connected with the social networking site Facebook.
There are 613 American billionaires in total.
However, the BBC reports that fast-growing rivals are challenging US dominance - Asia now has 332 billionaires, even more than Europe.