6. Jeff Bezos, Amazon
Net worth: $27.2bn ( £17bn)
One of the fathers of ecommerce, Bezos founded Amazon in 1994. He was named as person of the year by Time magazine in 1999. Last month Bezos bought the Washington Post for a reported $250m.
7. Larry Page, Google
Net worth: $24.9bn ( £15.6bn)
Page co-founded Google along with Sergey Brin while they were students at Stanford University in 1998. Initially a search engine, the firm has grown to encompass all manner of tech, from smartphone software to online maps.
8. Sergey Brin, Google
Net worth: $24.7bn ( £15.5bn)
Born in the Soviet Union in 1973, Brin moved to the US where he co-founded Google with Larry Page, one of his university peers. He has a diverse array of other business interests, from renewable energy to transport development.
9. Carl Icahn
Net worth: $20.3bn ( £12.8bn)
Activist investor” Carl Icahn has money in industries as diverse as entertainment, biotechnology and telecomms.
10. George Soros, Soros Fund Management
Net worth: $20bn ( £12.5bn)
Hungarian-born Soros founded hedge fund management firm Soros Fund Management in 1969 and has been particularly notable for his currency speculations. He is also known for his progressive political activism.