No stupid questions, just confused bloggers
Sunday, September 9, 2007
I don't carry a calculator, have never read Bill James, and barely survived high school math. That said, I'm a total stathead...at least for certain metrics. The good ones. Like PER.
A quick background on PER, for readers who've avoided ESPN.com the past year or Magic GM Otis Smith: It's John Hollinger's stat that combines "the good (made shots, steals, assists, rebounds, blocked shots, free throws), and subtracts the bad (missed shots, turnovers, fouls) by assigning a point value to each item." The figure is then adjusted on a per-minute basis and by the team's pace. It doesn't account for defensive presence, but it's a good barometer for offensive ability.
For example, when Raja Bell moved from the turgid Utah Jazz to the up-tempo Phoenix Suns, of course his scoring average went to nearly 15 ppg--there were plenty of possessions to go around and he played 37+ mpg. Writing for ESPN, Hollinger was less-impressed by Bell's "breakout season" and rightfully so; Raja didn't do anything different from his past performance, he just had more chances to do it. (amazingly, Raja's closest comparison, according to the database, is actually an old friend of ours).
(And yes, I love Raja as a defender and wish he played for the Wizards, but offensively, he's one of the weaker starting-2 guards in the league).
Similarly, Tim Duncan may average "only" 20 ppg (and you'd hear this argument last year, from stupid commentators who didn't think that was an MVP figure) but he's playing for slow-it-down San Antonio offense and just 34 mpg. His PER last year was 4th best in the league, which sounds far more representative of his value than his ranking on conventional lists (20th in ppg, 7th in rpg).
Look, PER isn't the greatest. If taken out of context, a bench player--who has a mini-scoring spree over a few minutes of garbage time--can look like Michael Jordan. But over the course of the season, players who rack up enough meaningful minutes can be accurately judged.
Anyway, what's this all about? Why question PER, a stat increasingly trusted by basketball fandom, in the middle of a football weekend? Well, Plissken at the Buzzer begged to differ with the formula. Here's the gist:
Plissken: Want to write about Lamar Odom. Lamar Odom=good. So why only 16.2 PER? No one understands PER. Pape Sow and Dajuan Wagner=better PER than Odom. PER lies. Give me conventional stats.
(Having seen the post, I immediately wrote a witty, clever rebuttal, as is my style)
perfect, but very good. Pape Sow and Dajuan Wagner misleading examples. Still best single stat in basketball, take with grain of salt.
There were pronouns and verbs too, but I'm lazy and want to get back to watching football.
Anyway, Tom Ziller--who pens the incomparable Sactown Royalty blog, which has the unfortunate distinction of being a Sacramento Kings blog--went and did me a lot better. Writing on BallHype, Ziller goes all "your argument, not so much" to Plissken, with convincing prose, anecdotes, and even a few graphics to defend PER's honor. Good stuff. More interestingly, it's drawn out a bunch of well-read sports bloggers, who reveal where they come down on PER (Jason Gurney: Pro. Miss Gossip: A little skeptical.) Much more interesting wedge issue than ethanol.
Anyway, if Hollinger, PER, or the whole idea of a
(Update: Cruc added the Plissken link earlier; here are a few others worthy of checking out, too. Thank You Isiah has a short, similar (dare I say, more incisive?) critique of Plissken, with a longer discussion in the comments. And juggernaut FreeDarko has gotten in on the conversation with an intriguing statistical analysis of PER inflation and deflation).
(Update on the update: Ziller's back with a sequel of sorts, breaking down what happens to role players' PER when they get more time. If clever stats and easy-to-read graphics aren't your thing, though, you can read our simplified summary here.)
posted by Doctor Dribbles @ 17:08,
- At September 9, 2007 at 7:29 PM, Ty Keenan said...
I realize the summary was somewhat tongue-in-cheek, but I'd advise anyone who wants to read about this stuff to check out the full Plissken post--our argument's more complicated than what the good doctor has presented here.
Doc Dribbles--did you see my responses to your issues with the examples Carter used? Does that clear it up, or do you still have a problem?
- At September 9, 2007 at 8:09 PM, Hot Shit College Student said...
Thanks for being meaner than me. PER didn't just fall out of the sky this summer, people.
- At September 10, 2007 at 3:58 AM, Carter Blanchard said...
Having fun tearing down straw men? I keed, mostly. I really don't mind people disagreeing with my point of view, and am glad it's led to this type of dialogue. I actually think that Ziller and I are much closer to being on the same page than it appears on the surface.
That said, I still don't think you get how I was using the Dajuan/Sow examples. I'm perfectly aware of why they are misleading, because that's exactly what I was pointing out: (like any other stat) it can often be misleading. Which is why I take issue with the goal of narrowing a player's contributions down to a single stat in the first place. To better understand a player's PER, you often need to know MPG, games played, etc. As kitchen sink metrics go, is it the best around? Sure. That doesn't mean it doesn't have issues worth exploring (and I'm not sure why, as HSCS points out, the fact that it's been around for a while would change that).
- At September 10, 2007 at 10:06 AM, Crucifictorious said...
Doctor Dribbles was out last night and tends to be tied up during the workday, so I doubt he's even seen your responses. (Nor do I plan to field your questions as well as Ty stepped in for Carter--Dribbles can fight his own battles). Will send him harassing e-mails so he gets on here and answers the firing line.
- At September 10, 2007 at 12:25 PM, Jarrett Carter said...
Bernard King should be the ruler of this stat.
- At September 10, 2007 at 3:00 PM, Doctor Dribbles said...
Wow--this conversation has really progressed. I don't know much I can add to it, given how far above my head FreeDarko has since pushed the argument, or even who I'm responding to between Ty and Carter. But as you did me the kindness of fielding my comments, here's my answer to yours.
First, I don’t think you and Ziller are on the same page. He gives you very kind props for the simplest part of your discussion, an argument that no one was making in the first place: That PER isn't the be-all, end-all of stats. Rather, Ziller's OK taking PER for what it is--an easy, imperfect catch-all--whereas (at least one of you) seems to resist the idea.
If your "main problem" is that the gradient of PER scores is confusing, well, I can't help you there. Hollinger has long publicized his relative ranking scores (which I even linked to in my post). And there's always context, even with the stats we know and love. Going across sports, what does it "mean" if a baseball player has 90 RBIs or 105 RBIs, or if a QB throws for 3,500 or 4,000 yards? For these raw stats, a lot depends on the system and the players around you, which is what PER helps equalize.
And, to a significant extent, the degree of performance excellence is always subjective. (If the Wizards had Reggie Miller and his 18.4 career PER, I'd be thrilled; Hollinger, meanwhile, thinks he comes up short of real greatness). But what does it mean for a starting pitcher to have a career ERA of 2.75 or 3.15? Or a football QB to have a rating of 95 or 101? You can trust that a certain stat is "the 10th highest all-time" or the "lowest in history," but really, all stats just fuel a larger conversation about any player.
Tearing down strawmen is an apt criticism, because that's exactly what your original post did. Beyond your test case of Lamar Odom, just six players are cited in your critique of PER (Bernard Robinson, Julius Hodge, Dajuan Wagner, Pape Sow, Brent Barry, and Earl Boykins). Respectively, two didn't actually have the PERs last season that you claimed; one played 7 total minutes, the other 34; and the other two, who were actually contributors, were backup guards. It's one thing if you kept the comparisons relevant, like Odom to Shawn Marion or even Antonio McDyess. But you never clarified that the scrubs never played; as far as I knew, based on the way you introduced the examples, Robinson and the rest played enough minutes for their PERs to be legit. And if I, who follow the NBA reasonably closely, didn't know how minutes Wagner played last year, how is the average reader supposed to grasp your purpose?
It's like me taking Joba Chamberlain's 0.00 ERA or LaDanian Tomlinson's 154.4 career QB rating and holding them up as legit, or more analogous to your argument, saying that ERA and QB rating stats deceive--without qualifying the tiny sample size. Why blame the stat category? Those guys produced in the limited opportunities given them; it's up the honest writer/blogger to provide the context upfront.
Otherwise, you're being disingenuous.
The intriguingly named Hot Shit College Student says it best: "What I still don't get, is why you're hellbent on dismissing PER because you've found that it's often misused. Why not have a beef with the people who are wrong?"
- At September 10, 2007 at 3:35 PM, Doctor Dribbles said...
Jarrett, PER doesn't love Bernard King as much as we do.
- At September 10, 2007 at 5:07 PM, Ty Keenan said...
You make some good points here, although I still think you're misrepresenting parts of the argument. I've made those points in other places, though, so I'd just be repeating them here. Anyway, if you want a full response, I'd be happy to give it--just let me know. Otherwise, I'd be happy to give you the last word.
I like your site, by the way.
- At September 11, 2007 at 8:57 PM, said...
This entire discussion seems to have progressed as if Dave Berri hadn't come out with the Wages of Wins, and didn't have a blog in which he lays out a completely different way of processing box score stats.
Isn't it possible that PER isn't a very good stat? That perhaps it dramatically overvalues scoring? And that we need not let PER cast a shadow over per-minute stats, basic mathematics, and common sense?
- At September 11, 2007 at 10:40 PM, said...
Anon the way PER treats scoring efficiency is quite consistent, I believe with the regression findings of Rosenbaum, Kubatko and Pelton discussed here
- At September 11, 2007 at 10:42 PM, said...
that is a FG% over about 40% begins to be a positive instead of the 50% that Berri uses.
But look at both. I prefer PErin general but will use PAWS/min especially for bigs.
- At September 12, 2007 at 2:00 AM, Doctor Dribbles said...
Various anons--Thanks for the suggestion re: Berri. I'm not a big believer in his system, to put it bluntly, but I think there's probably room by some bigger-brained blogger to analyze his and Hollinger's numbers in an understandable way.
And also thanks for the link to the paper by the Basketball-Reference guy (and company). Had heard of it, but to confess my ignorance, had never read it.
- At September 12, 2007 at 3:15 PM, said...
Glad the paper link was of interest DD.
I have said a few places that I think Value over Replacement, a stat available at basketball-reference.com is good as a measuring stick of relative player value over simply PER by itself because it incorporates actual minutes played and measures strength over replacement player in a way that top players see a larger separation from the merely above average.
- At September 12, 2007 at 8:45 PM, said...
Well here's my question:
Instead of starting with the premise "Odom is awesome, his PER is only slightly above average, so PER must be flawed," start by convincing me that Odom is significantly more than an above average-level productive forward able to stay out of foul trouble and in good enough shape to play a lot of minutes, THEN move to the conclusion that PER is bad. Because, frankly, I've never thought that Odom, especially playing un-inspired ball last year, was much more than an athletic guy who's a bit above average across the board.
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