Net worth: $47.9 billion

Age: 76

Country: US

Industry: Diversified investments

Source of wealth: Inheritance/self-made; Koch Industries

Along with his brother Charles, David Koch runs Koch Industries as executive vice president. The second-largest private company, $100 billion (in sales) Koch Industries manufactures everything from fertilizer and Dixie Cups to asphalt and biodiesel. David's personal wealth has decreased by $1.2 billion billion in the past year.

Famously conservative, the brothers also maintain immense political influence and routinely spend, along with their vast donor network, hundreds of millions on political campaigns and causes. 

David has had two brushes with death. He survived a plane crash in 1991 in which everyone else in first class died, and he also won a battle with prostate cancer. He's become one of the world's most generous givers since, pledging to contribute more than $1.2 billion to cancer research, hospitals, education, and cultural institutions over his lifetime through his David H. Koch Charitable Foundation.