Got a haircut today. Spent my time musing about the increased productivity of barbers. When I first went to the barbershop the barber used scissors almost exclusively, except for using a straight razor and warm lather to trim the areas around the ears and at the nape of the neck. Then they got an electric razor, which first was used to cut the sideburns evenly (what's a single sideburn). Today the barber used only a razor, even to trim my eyebrows.
Presumably the switch from scissors to razor means the haircut takes less time. But there's another reason for increased productivity: more time between haircuts. I think it's fair to say the universal standard for men in the 1940's was the standard haircut about once a month, except maybe for crewcuts (why doesn't the spell checker recognize "crewcut"). I'd assume these days there is no "standard" haircut. Maybe we're more standard than in the 1970's, when long hair was prevalent, but I don't think having the standard haircut is nearly as important now as in the 1940's. (I'll have to check the haircuts on Mad Men the next DVD we get.) So I'd argue that the average time between haircuts is longer today than it was during the 1940's, again increasing the productivity for barbers.
But declining standards for hair grooming isn't the only reason for increased productivity; there's aging. The male population is older these days, meaning the average male has less hair to cut and is also more experienced at receiving haircuts. I'm sure it takes longer for a barber to cut the hair of a 3-year old than a 73-year old.