6. David Koch

   

• Net Worth: $36 B                                                                       
• Source of Wealth: diversified, inherited and growing                 
• Citizen: United States
• Age: 73

David Hamilton Koch  is an American businessman, philanthropist, political activist, and chemical engineer. He is a co-owner (with older brother Charles) and an executive vice president of Koch Industries- the second-largest privately held company in the United States