I thought about a retired category. Then I thought when I retire, I'll still be an elevator service man and therefore I'll still be blue collar. Just not as tired.
Of course we're all professional at what we do. I considered Professional as a job category to be lawyers, doctors, vets, stock brokers, etc. Those who generally don't have blue collar people working directly under them like white collar management and executive positions.
I could see how an owner operator could fall into professional or self employed. That one could be disected for awhile.
A student would fall into the category of his major. I've been going to Stetson University of Law for almost 20 yrs. But I'm still just the elevator man.