What Makes a Billionaire? Forbes Answers

A college dropout, with geeky parents, who's born in Sept., is most likely to succeed.

Twenty percent of those who made a billion in IT lack a college degree, although billionaires working in finance typically have post-graduate qualifications, according to an analysis by Forbes.

Following up on its February listing of the World's Billionaires, Forbes has just published an analysis of those 657 self-made individuals to see what personal characteristics, if any they share.

Having parents who were good at math and, quirkily, being born in September, are commonalities among billionaires. Forbes notes: "The ability to crunch numbers is crucial to becoming a billionaire, and mathematical prowess is hereditary." Some of the most common, known professions of American billionaires' parents were engineer, accountant and small-business owner.

Among the IT billionaires Forbes lists who either never started or completed college are Microsoft's Bill Gates, Apple's Steve Jobs, Oracle's Larry Ellison and Dell's Michael Dell.