Forbes 2015 ranking of richest people:

1. Bill Gates $79.2bn (Microsoft)

2. Carlos Slim Helu $77.1bn (Phones and construction in Mexico)

3. Warren Buffett $72.7bn (Global investor)

4. Amancio Ortega $64.5bn (Zara and other fashion chains)

5. Larry Ellison $54.3bn (Oracle data storage technology)

6. Charles Koch $42.9bn (Industrialist)

7. David Koch $42.9bn (Industrialist)

8. Christy Walton $41.7bn (Walmart retail giant)

9. Jim Walton $40.6bn (Walmart retail giant)

10. Liliane Bettencourt $40.1bn (L'Oreal cosmetics firm)