The whiz-kid with an idea who vigorously taps out code while hyped up on energy drinks then launches a business to astronomical success is the exception, not the rule.

While that image is now embedded in American folklore thanks to names like Gates, Jobs, Bezos, and Dell, older entrepreneurs are now 30% more common than younger ones in America, according to new data from the Kauffman Foundation. For every 10 Mark Zuckerbergs (founders aged 20 to 34) there are 13 Reed Hastings (founders aged 35 to 44).

What’s more, the trend is accelerating. Young Americans’ drive to create new businesses declined this year to six-year low of 230 businesses per 100,000 adults. Entrepreneurship among those aged 55 to 64 and 35 to 44 each increased to 340 businesses per 100,000 adults, in 2012.

The Kauffman Foundation report measured the rate of individuals creating businesses each month as a percentage of adult, non-business owners at the start of that month. The data capture the formation of both incorporated and unincorporated businesses, where the business is the creator’s main job, irrespective of the number of jobs created.