I'm trying to find out about how many full-time tennis coaches there are in the U.S. It's for an article I'm writing. An estimate would be OK. The term "full-time" can be applied loosely and I'm not picky about it, but I'd roughly define it to be over 20-25 hours per week.
From Internet searches, I know there are 13,000 members of the U.S. Professional Tennis Association (made up of tennis coaches), and 19,000 high school tennis coaches.