The American and Canadian military are significant examples where many organizations are 'run' by people under 30. Yes, most field-grade and general officers, and senior NCOs are over 35. But, for example, the day-to-day decisions of logistics and tactics and technological is done by people between 19 and 27, by junior enlisted and company-grade officers.

I have never had as much responsibility an operational control over my job, in both fiscal and mission terms, as I had between the ages of 19 and 23 while in the military.