Look at this from a demand perspective: 300 mi American; 1/2 are men = 150 mil; say 1/3 don't go to barbers (bald, like long hair, "too good" for a barber, etc.) = 100 mil; 10 haircuts a year (round estimate) = 1 bil haircuts; each barber can handle say 10 (or other reasonable number) of haircuts a day = 3650 haircuts/barber; 1 bil haircuts demand/3650 for each barber = total number of barbers needed. (You probably don't have to do the math.)