The average American CEO is now 60. In 2000, they were 51. The corner office has aged nine years in 23 years. New CEOs are getting hired at 55, up from 48. Both lines moved the same direction at roughly the same rate. You don't see this in the public narrative because Zuckerberg and Altman make tech look young. The handful of founder-CEOs everyone tweets about are not in this dataset. The dataset is 50,510 hired professional CEOs across the U.S. economy. That's the actual picture of who runs…