18. Mark Zuckerberg

Title: Founder and CEO, Facebook

Country: US

Age: 31

The leader of the world’s largest social network had a prosperous year. In May, Facebook-owned virtual-reality company Oculus VR made a buzzworthy announcement: It will finally sell its first consumer headset, Oculus Rift, starting early next year. A few months later, Facebook announced for the first time that its site had a billion users in a single day and 8 billion daily video views, double the number it reported in April. The company's stock is up about 40% through November 2015, and as a result Mark Zuckerberg’s net worth has soared to $47.6 billion.

The Facebook founder also continues to invest hundreds of millions of his personal wealth in education, mainly through Startup:Education, a nonprofit he and his wife, Priscilla, founded in 2010 to improve schools in the Bay Area, and AltSchool, a company that promotes personalized education. He also gave $100 million to Newark, New Jersey's public schools, with disappointing results. After revealing in a July Facebook post that the couple is expecting their first child, they’ve announced plans to open a K-12 school in Palo Alto by next year that provides both education and health care to low-income families.