Baseball Crank
Covering the Front and Back Pages of the Newspaper
March 16, 2009
BASEBALL: EWSL 2009 Age and Rookie Baselines

It's time once again for my annual division previews using Established Win Shares Levels, which are explained here. Before we get to rolling out the 2009 EWSLs, I have to update the age adjustments and rookie values I use. These are based on the data I have gathered over the past five seasons, and so with each passing year, one would hope they become progressively more stable and useful (how accurate EWSL was in 2008 is another day's story, but of course as I always remind my readers, EWSL doesn't predict the future, it just provides a rough count of the talent on hand).

First up is the age adjustments; I've reformatted the table a bit from past years (see my writeups on the age adjustments following the 2004 season - also here - 2005, 2006 and 2007.

2008Non-PTotalNon-P
Age#WSEWSL%#WSEWSL%
21-0000433340.971
22446331.39424378194.91.940
2311931000.93046595462.51.286
24233532621.347831129873.31.293
25273713301.124115134810981.227
26272802571.089145158013931.135
27393513221.090163179017111.046
28384264280.995175211820591.029
29243303151.048155186219860.937
30282963090.958174188821560.876
31262283070.743154160619410.827
32394045240.771148151418410.822
33201472230.659115117014020.835
34232413170.760101103112010.858
35547550.85589678975.70.695
36192112520.83771673879.80.765
37772870.82848390594.30.656
38743650.66233274380.50.720
39213230.56526273347.80.785
40+636890.40430228423.70.538
All NP375398842980.928189920558219550.936

As you can see, there were the usual annual variations from historic norms, but the overall 5-year results are still pretty stable, showing that non-pitchers as a group improve rapidly in their early 20s, more slowly in their mid-20s, and begin a remorseless downward slide starting at age 29, with ages 35 and 37 being the worst culprits on the south side of 40 for one-year decline (if anything, the aggregate numbers conceal the extent of the decline because of people dropping out of the sample - note that a third of the guys who have jobs at age 30 are gone from the preseason depth charts by age 33). The interesting question is whether these trends have been skewed by steroid use; I note that in 2008, the decline rates for hitters in the age 31-34 bracket and the age 38-and-up bracket were unusually steep by historic standards. (The 35-year-old cohort was extremely small this year due to a lot of guys hitting the wall early). It was also a rough year for 23-year-olds, but that seems more like random noise.

I've included, for the first time, a total line for all ages at the bottom, and you can see that the average non-pitcher comes up 6.4% short of established levels in any given year. When you think about it, that's not really surprising.

2008PTotalP
Age#WSEWSL%#WSEWSL%
21-0000856381.474
22637351.05726192166.61.152
231073541.35247342327.81.043
24222221371.62080565498.41.134
25231391341.037108741669.41.107
26311811870.968135898839.21.070
27251942250.862127899944.60.952
2814731120.652137943956.30.986
29312592600.99613891410360.882
30301511910.791128742870.40.852
31251811751.034109715836.50.855
3215941130.83284495676.50.732
3314761220.62371380544.30.698
34614320.43856262386.60.678
35635390.89744206314.20.656
36950680.73539219254.20.862
37831510.60833223264.30.844
38645550.818342342930.799
39223151.53321164177.30.925
40+13681190.57155398539.30.738
All P296194621240.91614809588106330.902

The pitchers are by nature more volatile - you will notice that the average pitcher is apt to be off closer to 10% over the 5-year period. It was a freakishly good year for 23-24-year-old pitchers, as well as age 31 and age 39 (the latter being basically Mike Mussina), and crummy for everyone else; the age 28 and 34 groups, already smaller than their surrounding age cohorts, got slaughtered. The overall 5-year pattern remains one of decline for pitchers in every age group above 26, with brutal attrition rates beyond age 32. Pitching is rough business.

Type of Player# in 2008WS in 2008# 2004-08WS 2004-08Rate
Everyday Players101045258511.25
Bench Players (Under 30)44441593.61
Bench Players (Age 30+)10320.67
Rotation Starters41618774.28
Relief Pitchers0011655.91
TOTAL191241288886.94

The rookie adjustments remain, along with the ad hoc fudge factor, the most glaringly unscientific part of this enterprise, but I need some less than wholly random way to plug in the rookies, and at least for everyday players the rough guideline that has them around 11 Win Shares a year for rookies with everyday jobs mostly holds up. Rookie starting pitchers, of course, will break your heart.

Posted by Baseball Crank at 9:22 AM | Baseball 2009 • | Baseball Studies | Comments (0) | TrackBack (0)
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