Tom Doak:
Actually, the ball was rolled back when the size and weight rule was instituted in the 30's.
If you read O.B. Keeler (Autobiography of an Average Golfer) he talks about the different balls that were in use and how the pros were using balls that they could drive 30-50 yards past the best "amatuer" drives. There is also a great article by Bobby Jones in American Golfer complaining about the balls, that all the par fours were becoming a Driver, Mashie Niblick (he played a 45 degree Mashie Niblick, about equal to a current 9 or PW).
Keeler also quotes carry distances that are very enlightening as are a number of golf instructionals of that era.
This had also going on in the gutty era as a couple of pro's could obtain drives in excess of 300 yards on command and the feat was attributed to the balls. (I can look up that book if someone wants to know more, I think it was Hutchinson)
In the collecting community there has been some talk of x-raying balls to find examples of leaded balls.
So there is a case to be made for the ball having been "rolled back" in performance in the past.