In today’s NY Times Keeping Score column, several Penn economists are critical of “the Roger Clemens report”. In particular, the authors feel that comparing Clemens to three excellent pitchers who excelled late in their careers is a dodgy tactic.
A better approach to this problem involves comparing the career trajectories of all highly durable starting pitchers. We have analyzed the progress of Clemens as well as all 31 other pitchers since 1968 who started at least 10 games in at least 15 seasons, and pitched at least 3,000 innings. For two common pitching statistics, earned run average and walks-plus-hits per innings pitched, we fitted a smooth curve to all the data from these 31 pitchers and compared it with those for Clemens’s career.
Relative to this larger comparison group, Clemens’s second act is unusual. The other pitchers in this durable group usually improve steadily early in their careers, peaking at around age 30. Then a slow decline sets in as they reach their mid-30s.
Clemens follows a far different path. The arc of Clemens’s career is upside down: his performance declines as he enters his late 20s and improves into his mid-30s and 40s.
I have a few comments. First, the reason his career is upside down in terms of WHIP is because of his walks. Clemens’s career pattern in preventing walks is bizarre, as I previously documented, but walks are not the thing I think of when I think or performance gains from steroids.
On the other hand, his strikeout performance did decline with age, which means that the decline in walks likely was not the product of being able to pitch more in the zone.
The authors are also critical of the Clemens Report for using ERA because “a pitcher’s E.R.A. is affected by factors, like defense, that have nothing to do with his pitching.” But, using WHIP doesn’t solve this, because all hits except home runs involve the defense.
As to the comparison with other pitchers who excelled at advanced ages, this is not meant to demonstrate Clemens’s performance path was expected. Clemens’s aging pattern is certainly atypical. See Cy Morong’s evaluation of an aging cohort that includes Clemens. What these comparisons do convey is that such performances have been observed before, and therefore just because Clemens performed in this way doesn’t mean that steroid use is the only possible explanation. Clemens aging pattern is not the norm, but it is also not odd enough to prove anything.
Finally, I’d like to reiterate that Clemens’s most suspicious late-career spike (2004-2006) occurred at a time when McNamee was working for Clemens but had no knowledge of steroid use. It would be odd that he would get the drugs from McNamee in 1998, 2000, and 2001; but then find another source. And given that I don’t find McNamee to be a compelling witness, I am inclined to believe Clemens pitched clean until I see some better forensic evidence.
The authors, for whom I have great respect, bring something interesting to the table, but I don’t interpret the findings to be an indictment Clemens. Although, I agree with them that the Clemens report is not a compelling document. I think it was unnecessary, and it has served as a focal point for criticism rather than to exonerate the pitcher.
Addendum: I received an e-mail from Randy Hendricks explaining some of the impact that the Clemens report did have, particularly in dispelling the common misperception that Clemens was done in 1996. I guess I was a bit narrow-minded in my interpretation, since I already knew this. Thus, I was incorrect in calling the report unnecessary.