The thought process behind the Bill James systemby Derek Carty
January 18, 2010
|Are the Bill James projections for a guy like Matt Holliday directly comparable to other systems after all? (Icon/SMI)|
As I'm in no way affiliated with James himself, the projections, or Baseball Info Solutions, there were some things I wasn't entirely clear on and some questions I couldn't answer. Luckily, a member of the BIS team who works on the projections (Ben Jedlovec) read the article and was kind enough to offer an explanation for some of the things I and the THTF readers noted. I'll post his two e-mails in full.
I saw your article today on the Bill James projections and wanted to say that I enjoyed your perspective. As someone who had a hand in this year’s BJHB projections, I wanted to add a couple more thoughts for your consideration.
First off, we are admittedly optimistic with playing time projections, especially in the Handbook edition of the projections. The thought is to give the reader an idea of what we think a player can do if given a full season of plate appearances. We could project Jason Heyward for 200 ABs with a couple homers, but that doesn’t tell you much about what we think of his ability. We want to give him a full season of ABs to show you what we think he can do if he gets a chance.
Also, it may seem that we have a high run environment. Part of this is due to the fact that we don’t project every marginal major league bench player who will accumulate 100 or 200 ABs over the course of the season. Chances are, some of the guys we project for 500 ABs will get hurt, and 300 ABs will go to a more marginal player or a reserve who we don’t have projected. Of course this will decrease the run environment.
Keep up the good work at THT,
Baseball Info Solutions
And here's the second one:
After reviewing the comments on your original article, I wanted to mention one more thing in case you do a follow-up piece: Bill is most certainly still involved in the projections. He and John Dewan worked on the original coding shortly after BIS began publishing the Handbook, so most of the work is just the mechanics of running the code. Any changes to the code are instituted by Bill and John, and Bill, John, Steve Moyer, and others review the projections at least twice each and make manual playing time adjustments before we run the final version for the Handbook.
Beyond that, I'd just reiterate what I said earlier.
Take 10 elite hitters with a similar health record- say nine of them will get 600 ABs and the other (we don't know which one ahead of time) will get hurt in the spring and get zero ABs. We could regress them all and give all 10 550 ABs, meaning we're selling nine guys a little short and missing big on the 10th. Or, we can project all 10 for 600 ABs, sell nobody short and missing big on the same guy who was injured.
The second approach will get you a higher run environment, of course.
For fantasy baseball, you could make a strong argument for the second approach. Both methods will miss on the one injured player, but the first approach sells nine other guys short. If both systems are roughly equal assessments of player ability (prorated to a certain number of ABs), why would you use the first one?
ON AVERAGE, the first approach will be spot on. However, the second approach will be better nine times out of 10. This is another case when the average (expected value) doesn't give the full picture. It depends on what you're looking for, I guess.
So there you have it. Some insight into the thought process behind the Bill James system from someone working on the inside.
Given what Ben says about the inner-workings of the Bill James system, it appears that the projections for most veteran players should indeed be comparable between projection systems (at least as far as any projection system goes — they all assume a slightly different league average from each other). The James system might only seem more optimistic because: 1) they actually are optimistic about some rookies, 2) the run environment is inflated because a lot of veteran bench-type players don't get projected, and 3) the run environment is further inflated (over previous seasons) because the system doesn't attempt to forecast injuries, opting to give a relatively higher number of players a full season of at-bats.
Whether or not this means we actually can compare, say, Alex Rodriguez's Bill James projection to his CHONE projections isn't 100 percent certain — we'd need to run some tests, as we would with any other fantasy baseball theory — but I think Ben provided us with some very interesting food for thought.
As always, if you have any questions or comments, feel free to let me know.
Derek Carty, 23, has also been published by NBC's Rotoworld, Sports Illustrated, FOX Sports, and USA Today. This season, he'll be contributing to FanDuel and will be linking to all of his work at DerekCarty.com. In his three years competing in expert leagues, he has won 2 titles with 4 top three finishes, including a LABR NL title in 2009, making him the youngest person to ever win a major expert league title. Derek is a proud graduate of the MLB Scouting Bureau's Scout Development Program and is a firm believer in the importance of combining stats and scouting. He welcomes questions via e-mail, Facebook, or Twitter.
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