Plutocrats: Who are the richest of the rich?
24 January 2013 Last updated at 15:35 GMT
The super-rich are often referred to as the richest 1% of the population - whose wealth surpasses the other 99%.
But now there is a separate elite, the 0.1%, who tower above even the multi-millionaires.
Chrystia Freeland - author of Plutocrats: The Rise of the New Global Super-Rich and the Fall of Everyone Else - and Anup Desai, a City University of New York professor involved in the Occupy movement, spoke to the BBC's Mishal Husain about the growth of the billionaire class, and what that means for the wider economy.