Wednesday, November 26, 2008
Rob Neyer touts wOBA
Here is the blog entry:
http://sports.espn.go.com/espn/blog/index?name=neyer_rob
For a change, there are some good comments/suggestions about the merits and demerits of wOBA and whether it will or should be “mainstream.” I say “for a change” only because unfortunately (given the good quality of the articles) the quality of the comments/discussion on Rob’s blog is generally poor. I guess that is because ESPN.com is a “mainstream” site and tends not to get the ‘serious’ sabermetrically-oriented fan. Or at least most of the fans are not.
Anyway, feel free to discuss the pros and cons of wOBA. It was Tango’s creation and introduced in The Book.
I tried to write someting to Rob using either the comments section or the mailbad and it didn’t work; in lieu of that I’ll post it here so at least someone reads it:
*****
Dear Mr. Neyer,
My name is Colin Wyers and I’m writing in response to your blog entry on Tango’s wOBA, specifically:
“Meanwhile, the Baseball Prospectus metrics are—last I checked, anyway—completely opaque. Because BP is a for-profit enterprise that holds its intellectual property closely, we’re just supposed to trust them.
Which I do, generally. But that science-vs.-enterprise dynamic can be tricky. The methodology behind BP’s metrics is not, to my knowledge, peer-reviewed. If one or two people make a big mistake, would anyone else know? Now, let’s jump ahead and say that two or three years down the line, the big mistake was discovered internally. Would BP announce to the world that all those numbers over the previous three years had been wrong? Or would the guys running the show decide that the loss of credibility (and potentially, revenues) isn’t balanced by the loss of integrity?”
This is not - precisely - true, and your hypothetical scenario isn’t quite hypothetical. Essentially, everything that makes up EqA has been published by Baseball Prospectus in some form or another at some point in time - I can and have figured it (and MLVr, the rate stat that forms the basis for VORP) on my own using the published explanations by BP writers. Certainly it’s a bit obfuscated (I once spent an entire afternoon crawling through the old rec.arts.baseball USENET archives for Woolner’s original writings on VORP) but if the construction of BP’s offensive metrics is supposed to be a secret at some point they slipped up.
The problem is that there are issues with the methodology behind both of them, MLVr moreso than EqA. The issues with EqA are a bit difficult to explain without some pretty hairy math that I’m not the best person to explain, and aren’t a major issue. The problems with MLVr are more deep-rooted and unsettling (MLVr criminally underrates the walk, for instance). None of this is exactly secret - I know Tom Tango, Patriot and myself have written about several of these issues in the past, and I haven’t gotten a response from anyone at BP on the matters. Clay Davenport seems to be responsive to some of these concerns - Tango says he’s talked to him before about it. You’d have to ask Tom to be sure, but I don’t think anyone’s said anything substantial about fixing MLV/VORP’s issues.
I don’t want to try and impugn anyone’s motives here - I don’t pretend to know why BP isn’t responding to these sorts of concerns. (If I had to hazard a guess, I’d say it’s because a lot of the people best qualified to deal with these questions have matriculated - either to MLB teams or in Silver’s case to his career as a political analyst.)
In the end, I’d say the big benefit of wOBA over EqA is that the math is a lot simpler - calculating wOBA is simpler than EqA, and figuring a player’s runs from wOBA is much, much simpler (to do it the “correct” way with EqA requires using exponents and is a bit sticky). You do lose some of the nice benefits of the Davenport Translations, like park factors and league adjustments.
As far as non SB/CS baserunning metrics, there are quite a few out there - BP has one (probably the best one out there), although it’s not very well integrated with their other offerings. Bill James Online has one. Lee Panas publishes some on his Tigers blog. I’ve dabbled in it before myself. I think this is one of those things that simply hasn’t percolated all the way yet, and will be pretty common in one or two years - the data and the methods are both available.
Cheers,
--CW