That’s how many billionaires there are worldwide, and more than half of them are self-made. This according to Forbes‘ annual ranking of the richest of the rich. During the last two years, 215 new people joined the club? Why so many new members?

In part, the rich can thank improved global economic factors for their swelling fortunes. Bullish world stock markets, a weak dollar and surging commodity and real estate prices have all played a part. But so has old-fashioned entrepreneurialism. Take Google. In the seven years since its founding, two Stanford graduate students have grown a computer science project into a world-class corporation, with a market capitalization of nearly $49 billion. Along the way, they have become billionaires, seven times over.