The legends of Bill Gates, Steve Jobs, Mark Zuckerberg and other high-tech entrepreneurs have fed a stereotypical vision of innovation in America: Mix a brainy college dropout, a garage-incubated idea and a powerful venture capitalist, stir well, and you get the latest Silicon Valley powerhouse. That’s Hollywood’s version of technological innovation; unfortunately, it’s also the one that venture capitalists try to fund and government planners seek to replicate. But these individuals are not America’s typical entrepreneurs. To find them, first let’s dispense with some major misconceptions about where our best ideas comes from.

1. America’s typical tech entrepreneurs are in their 20s.

My research team at Duke University has studied the backgrounds of the country’s entrepreneurs, and our findings debunk this popular notion. Our 2009 survey of 549 company founders across a dozen fast-growth industries found that, in fact, the average and median age of these founders when they started their companies was 40.Twice as many were older than 50as were younger than 25; twice as many were over 60as under 20. Seventy percent were married when they launched their first business; an additional 5.2 percent were divorced, separated or widowed. Sixty percent had at least one child, and 43.5 percent had two or more children.

Entrepreneurs are motivated to take the risk of starting a venture because they get tired of working for others, have ideas for new businesses based on the experience they gained working for others or want to strike it big before they retire. The mythology of the kid in the garage is grounded more in Hollywood than in Silicon Valley.

2. Entrepreneurs are like top athletes: They are born, not made.

Silicon Valley investors such as Jason Calacanis proudly proclaim that successful entrepreneurs come from entrepreneurial families and start off running lemonade stands as kids. After meeting Wharton Business School...