Mark Zuckerberg with Facebook, Paul Allen and Bill Gates with Microsoft, Steve Wozniak and Steve Jobs with Apple AAPL +3.52% —those success stories lead some people to think that coming up with big ideas is a young person’s game. But the tech entrepreneurs who rose to early fame and fortune are just the outliers. The typical entrepreneur is a middle-aged professional who learns about a market need and starts a company with his own savings. Research that my team completed in 2009 determined that the average age of a successful entrepreneur in high-growth industries such as computers, health care and aerospace is 40. Twice as many successful entrepreneurs are aged over 50 as under 25, and twice as many over 60 as under 20.