February 26, 2007
BASEBALL: Age and EWSL, 2004-06
This is Part III of my look back at at how Established Win Shares Levels fared in 2006. It's time to look at the age adjustments. (I've looked at these previously here, here and here).
The great thing about doing something like EWSL as an ongoing project is that the data becomes progressively more stable over time: I now have three years of results to work from in evaluating how players tend to perform at each age relative to their adjusted Established Win Shares Levels, and thus can have progressively more confidence in the age adjustments I use going forward. For example, the more years of data I have, the less influenced it will be by a single generation of exceptional players born in a particular year.
Let's start with the 3-year results for the non-pitchers:
As you can see, the rapid rise of young players and their gradual fall from age 29 on is a powerful pattern, and one that grows smoother with each year's additional data. 2006 was a good year for 27-year-olds and a bad year for 28-year-olds, so some equilibrium has been restored in that regard from the prior age adjustments showing 27-year-olds flatlining but then hopping up one last time at 28. After age 32, the number of players holding jobs really starts to drop off.
The train wreck at age 35 only grew more pronounced this season. On the other hand, additional data helped bouy up the 40+ year olds, whose numbers got devastated by Barry Bonds' 2005. Here's this year's data on its own:
As I've explained before, the nature of any established performance level will exaggerate the upward and downward trajectory of player aging, since a 25-year-old is still being partly compared to his 22-year-old self, while a 35-year-old is still being partly compared to his 32-year-old self.
Now, the pitchers:
2006 was a tough year for the established pitchers, at least the under-30 set. The one-year sample sizes get really small - for example, Jon Lieber was the 36-year-old starting pitcher, Steve Trachsel and Paul Byrd the only 35-year-old starters. In general, the rule still holds that the pitchers as a group start to fall off earlier than the hitters. The 2006 data:
Overall, as consistent with past data, the age/EWSL numbers are a powerful reminder of the tides of age pulling players down from 29 onward. Which is not surprising: in baseball, as in life, everyone comes up from nothing and goes back to nothing in the end.
I've always believed, but cannot figure out how to prove, just how much the decline at 29 or so is as much years of service as it is years of age. The study you show Crank is what is expected in a way. You start at 21, with few players, and of course, it grows. Unlike basketball, a 23 year old baseball player is considered very young. So setting a bottom limit of 21 is about where you can go. And by 32, the bottom drops out. So my question is:
Is it just being 32, or is about 10-11 years what you can expect your body to produce? I think of Junior Griffey as someone who comes quickly to mind. I wonder about ARod, and haven't taken it much further. But in the end, was Griffey just injury prone, or was he reaching a limit that he got to younger because he started younger. I guess you could look at how many 18 year olds started. They would have to be great or they wouldn't have jobs (except maybe someone like Joe Nuxhall and Ed Kranepool), but guys like Feller, Gooden, Ott, Kaline. Not enough players probably for the data to have any meaning, but just wondering...
re: age-related decline
this data continues to confirm the pattern of age-related decline that Bill James first uncovered in his published work (or which he was the first to widely publish since others also were working on the topic) in professional baseball which shows that a baseball player reaches peak performance usually at age 28 and thereafter will suffer age-related decline, and sharp decline after age 35. The decline will be sharper for non-superstars than for superstars.
The expression of the decline in terms of win shares and expected win share levels completes to a certain extent the theory as it was first formulated by James and others.
These are important numbers. For example, what should be expected of a rookied like Ryan Howard, who came late to the bigs at age 25, after his second year of service? Obviously, that he will develop for three more years, and then start to decline. But since his arbitration and free agent years are three years away, it suggests that it would be imprudent to sign him to a long year deal if his skills are to decline. on the other hand, they are the declining skills of a great player.
These are the kinds of questions that this type of analysis can help solve.
Will Chase Utley decline sharply in the back end of the long deal the phils signed with him? Well, probably--though they are out of it before he hits 35.
these and other burning questions for the hot stove league.
--arthur j kyriazis, philly