Timelining

Are the players of today better than players of the past? If so, how much better? These are not easy questions to answer. It is possible to construct a study to estimate it. David Gassko did such for The Hardball Times two years ago, and did a good job, producing very reaonable results. Unfortunately, it is far from conclusive and very sensitive to whatever assumptions you use to set it up.The approach, which I have played around with, is to compare how players do from one season to the next. But how much of it is age decline, and how much is the change in league strength? You really can't tell, since the same process we're using here is what we use to compute aging factors in the first place.It is necessary to regress to the mean as well. Take two average players, but one is +15 by luck and the other is -15 by bad luck. The next year, player 1 should be average. But player 2 may not play, or else be limited to a bench role, so as a group you would see decline even...