Earlier today I blogged about a battle of the basketball statisticians, in which David Berri, and even Malcolm Gladwell, criticized the work of John Hollinger. John Hollinger responded by e-mail. From my inbox:

Henry,



I've been trying real hard not to say anything about Wages of Wins, because it would only come across as self-serving to knock the work of another person in the field.



But now that a shot has been fired across my bow, I have to defend myself.



Berri leads off with a huge misunderstanding of PER -- that the credits and debits it gives for making and missing shots equate to a "break-even" shooting mark of 30.4% on 2-point shots. He made this assumption because he forgot that PER is calibrated against the rest of the league at the end of the formula.



Actually, if we took a player was completely average in every other respect for the 2006-07 season -- rebounds, free throws, assists, turnovers, etc. -- and gave him a league-average rate of shots, and all

of them were 2-pointers, and he shot 30.4%, he'd end up with a PER of 7.18. As long-time PER fans know, that would make him considerably worse than nearly every player in the league.



To end up with a league-aveage PER of 15,00, the actual break-even mark in this case is 48.5%, which is exactly what the league average is on 2-point shots this season.



Secondly, regarding Gladwell's comments on Berri's ranking of players like Ben Wallace and Dennis Rodman (as well as several other less famous players who also got piles of rebounds), the issue isn't the discovery of some new Holy Grail of basketball analysis, but rather the result of an assumption in Berri's formula that distorts their value.



Namely, that his formula equated a rebound as being just as valuable as a steal, and a missed shot just as damaging as a turnover.



While this made his sums work in the aggregate, for individuals it threw things way out of kilter, as it overrewarded rebounders and overpenalized guys who miss shots.



And it seems clearly mistaken, both because missed shots can be rebounded while turnovers can't, and because a defensive rebound is merely the completing piece of a sequence that began by forcing a missed shot.



Like I said, I was really hoping to hold my fire on this, but the latest missive compelled a response.



Keep up the good work,



John

UPDATE: Berri responds on his blog. You should really take some time and investigate the multi-faceted debate that is now also playing out. It's pretty bitter (at one point, Berri takes on Hollinger for saying that he wanted to stay out of this). There's also pretty heated debate involving Dan Rosenbaum in the comments of the Gladwell post and on Berri's blog. There's enough there to make your head spin. One of Berri's commenters, Erich, deserves the last word:

I am all for competition and statistical validation. That being said, I do not like the way this is playing out. From the combative conversation to the lack of cooperative learning, basketball’s statistical analysis fans are losing on all fronts.



It seems childish to have to go through a third party (Gladwell) and the language used so far has appeared to me as combative rather than constructive.



Given that we are in the early stages of understanding basketball by the numbers, any methodology should still be evolving, and therefore we should not fiercely defend it nor bash another evolving model.



I’d like to see a cooperative competition to advance all of basketball understanding. If each system (Beech, Berri, Hollinger) were to make open predictions, basketball analysis as a community can analyze the results and suggest continuous refinement to each model, furthering our total understanding as individuals and as a group.



I believe each model brings something to the table now. I like how Hollinger was able to produce in-depth preseason projections. Even if he was forced by ESPN’s department requirement, his projections ranked all NBA teams and were stated confidently.



Out of Berri’s model, I have enjoyed his easy-to-employ formula in analyzing NBA draft prospects and NCAA basketball. His formula generated my love for Paul Millsap which has so far been validated with his outstanding play.



Overall, basketball analysis is still in its infancy. We are all seeking the same thing. Lets take a deep breath, shake hands, and put this competition on the court. Develop rudimentary prediction systems and let the numbers play themselves out. Engage in constructive criticism with open minds and open communication. Basketball analysis can only benefit from such an arrangement.