It’s a problem that leaves brows furrowed on barstools across the world: how to rate the sportsmen and women of the day against the stars of yesteryear.
There’s no easy way to make meaningful comparisons when sports change so dramatically over the years. Even in endeavours like baseball where player stats have been meticulously kept for almost a hundred years, comparisons across the decades can be odious. Is it really fair to compare players from the 1920s against those of the last 20 years when so many external factors have changed such as the use of new equipment, better training methods and, of course, performance enhancing drugs?
In 1914, the National League Most Valuable Player was Johnny Evers with a batting average of 0.279, 1 Home Run and 40 Runs Batted In. That was impressive then but these stats would embarrass even a second rate player in today’s game.
But what if there were a way to remove the systematic differences to reveal intrinsic talent? Today, Alexander Petersen at Boston University and a few pals explain just such a method that “detrends” the data leaving an objective measure of a player’s raw ability.
The detrending process is a statistical trick that essentially rates all players relative only to their contemporaries. This effectively cancels out the effect of performance-enhancing factors which are equally available to everybody in a given era. The detrended stats then allows them to be objectively compared with players from other eras and the end product is a ranking of pure talent.
Petersen and co compare the detrended rankings against the traditional ones for several standard baseball metrics, such as Career Home Runs, Season Home Runs and so on.
The results will be an eye-opener for some fans and Petersen and co provide an interesting commentary on the new tables. For example, their new list of the top 50 individual home run performances by season does not contain a single entry after 1950. Not even the performance of Barry Bonds in 2001 or of Mark McGwire in 1998 make the list. In fact, Babe Ruth’s achievements from the 1920s fill seven of the top ten slots.
Petersen and co are at pains to point out why this is: “It behooves us to point out that these results do not mean that Babe Ruth was a better slugger than any other before or after him, but rather, relative to the players during his era, he was the best home run hitter, by far, of all time.”
The Boston team say their method can be applied to other sports with professional leagues such as American basketball, Korean baseball and English football. And it also works in ranking research scientists too.
Petersen and co may not actually settle any barstool brow-creasers with this paper but they’ve clearly had some fun in trying.
Ref: arxiv.org/abs/1003.0134: Detrending Career Statistics In Professional Baseball: Accounting For The Steroids Era And Beyond