This is an excellent point at the lower end of this age range. I do still think there is something in the fact that today's tech companies have very high profit

This is an excellent point at the lower end of this age range. I do still think there is something in the fact that today's tech companies have very high profit-per-employee numbers. This allows them to pay higher skilled workers more money and those people become less likely to leave and start something on their own (a financially risky choice). It's possible that golden handcuffs (equity, etc.) are pushing this number down as well.