Yes, most unemployed people are probably much older than 18. However most people making the decision to go to college, or go into various trades, are 18 or younger. That seems to be the age bracket Mike Rowe is primarily talking about.
The specific example was about a large influx of trainees into post Katrina Louisiana. That is the scenario I was mainly talking about.
The general point about kids not necessarily needing to go to college, I 100% agree with. Though, all of the numbers I've ever been shown do paint a picture that statistically you are better off doing so than not.
