America's wealthiest are worth more than ever - with the top 400 billionaires worth a breataking $2.3trillion, according to the latest edition of the Forbes 400. The renowned rich list was again topped by Bill Gates - the richest American for the past 21 years - whose fortune was $81.2billion. But the Microsoft founder, 58, had newer technology billionaires snapping at his heels, including Facebook CEO Mark Zuckerberg, who broke the top 10 for the first time having gained $15billion in the past year. Scroll down for the top 40 and the size of their fortunes Old tech, new tech: Bill Gates, the Microsoft founder, topped the Forbes 400 with his $81.2billion fortune, while Facebook CEO Mark Zuckerberg, 30, hit the list's top 10 just a decade after founding the social network while in college
@highlight
New heights for wealthiest 400 Americans, with rankings starting at $1.4bn
@highlight
Bill Gates was top of the list for the 21st year, with $81.2billion to his name
@highlight
Newer figures in technology advanced quickly - including Mark Zuckerberg
@highlight
Facebook founder and CEO was ranked number 10 with $34billion fortune
@highlight
Top 400 were largely the same people thanks to buoyant stock market
@placeholder of the pile is Mark Zuckerberg, whose $34billion fortune sees him at spot 10 on the list aged just 30.