You cannot just look at percentage as the only number you look at. Think about it this way, if you get a raise of $1 per hour each year. If you start at $15 dollars an hour the raise equals about 7% but the next year when you get the raise because the starting point is now $16 dollars an hour the increase is now less percentage wise it is now only 6%, then the next year the percentage increase is even lower is only 5% and so on and so on. So Yes in the 40s and 50s the percentage increase for Watchtower was greater because they had a smaller starting number, but as that starting number gets bigger, unless the amount of people you add gets bigger at the same rate the percentage is still the same.
I am not saying that Watchtower doesn't have a increase problem, but you cannot solely look at the percentage increase.