Edward Lazear writes,

we found that young societies tend to generate more new businesses than older societies. Young people are more energetic and have many innovative ideas. But starting a successful business requires more than ideas. Business acumen is essential to the entrepreneur. Previous positions of responsibility in companies provide the skills needed to successfully start businesses, and young workers often do not hold those positions in aging societies, where managerial slots are clogged with older workers.

Pointer from Mark Thoma. Another interesting quote from Lazear:

The importance of youth is illustrated by the stark contrast between two neighboring countries, Japan and Korea. Using the GEM survey data, we found that Japan’s rate of entrepreneurship (the proportion of individuals who own a business that they founded in the past 42 months) is just 1.5%. In Korea the rate is a much higher, 8%. The median age in Japan is 43; in Korea it is 34. The U.S., with an entrepreneurship rate of 4.4% and a median age of 36, is in the middle of the pack on both entrepreneurship rates and median age.