There are a lot of theories about how old you "should" be to found a startup.

Some people say younger is better. You're young and strong and can withstand lots of sleep deprivation and keep going. You're more likely to take risks and less likely to quit (supposedly).

On the other hand, wisdom comes with age. The older you are, the better you know your industry, and likely more than one industry. You have strong connections and a lot of experience.

So which is it?

The facts clearly suggest one side over the other. According to studies out of Duke University, the Kauffman Foundation, the Founder Institute, and Northwestern, the average entrepreneur is actually 40 years old when launching his or her first startup--and the average age of leaders of high-growth startups is 45 years old.

That's right: While tech publications are rife with stories of crazy-successful 22-year-old founders who become billionaires, the truth is that 40-somethings are much more likely to start companies--and succeed.

Adeo Ressi, founder of the Founder Institute, puts it succinctly: "The research shows that an older age is actually a better predictor of entrepreneurial success."

The research in question isn't small scale. To get its data, the Founder Institute tracked 3,000 global applicants; examined in detail the progress of the organization's 1,000 enrolled founders; and tracked their 350 graduates.

Why does age help? According to Ressi, "Older individuals have generally completed more complex projects--from buying a house to raising a family. In addition, older people have developed greater vocational skills than their younger counterparts in many, but not all, cases," he says. "We theorize that the combination of successful project completion skills with real-world experience helps older entrepreneurs identify and address more realistic business opportunities."

This is borne out not only by the research (which shows, among other things, that people over 55 are twice as likely to launch a high-growth startup as those under 35), but by scanning just a quick list of successful entrepreneurs:

  • Anne Wojcicki was 33 when she founded 23andMe
  • Ray Kroc was 52 when he shaped McDonald's into a multibillion-dollar behemoth
  • Sam Walton was 44 when he started a little company called Walmart
  • Lynda Weinman co-founded at 40 (and then sold it to LinkedIn for $1.5 billion)
  • Bernie Marcus co-founded Home Depot at 50

Not a 20-something among them.

The fact is, American culture venerates youth and denigrates age. This is damaging to everyone. It damages older individuals by making them feel useless or "expired" once they hit a certain age. And it damages younger people by making them feel like they've failed if they haven't founded Snapchat by the time they're 24.

Yes, of course there are very young people who become successful entrepreneurs. But it's extremely misleading to believe this is the norm, or that you're behind if you're 32 and haven't made your biggest contribution to the world yet.

Researchers out of Northwestern minced no words when they described their results: "Many observers, and many investors, believe that young people are especially likely to produce the most successful new firms. The researchers use administrative data at the U.S. Census Bureau to study the ages of founders of growth-oriented startups in the past decade. Their primary finding is that successful entrepreneurs are middle-aged, not young. The mean founder age for the 1 in 1,000 fastest-growing new ventures is 45.0 ... These findings strongly reject common hypotheses that emphasize youth as a key trait of successful entrepreneurs." (My emphasis.)

Encouragingly, according to Duke University researcher Vivek Wadhwa, when it comes to becoming a successful entrepreneur, anyone can get into the game: 

The majority [of successful entrepreneurs] didn't have entrepreneurial parents. They didn't even have entrepreneurial aspirations while going to school. They simply got tired of working for others, had a great idea they wanted to commercialize, or woke up one day with an urgent desire to build wealth before they retired. So they took the big leap.

Don't ever let anyone tell you it's too late to start.

Don't get discouraged if you're still young and you're "not there yet."

Just keep swimming. And when your big flash of inspiration hits ... take the big leap.