Letting the Lamppost Illuminate
He uses statistics as a drunken man uses lamp-posts…
For support rather than illumination
Andrew Lang (1844-1912)
I’ve been rather crucified lately for having Kobe Bryant so low on my MVP list, and I completely understand why. He’s the player many consider to be the best in the game, his team has an elite record, and as we approach the final stretch of the regular season, both he and his team appear to be entering back into their familiar, championship-winning groove. How can he be not anywhere near the top 5 in the MVP race?
And I answer, knowing that my response hurts my credibility among quite a few not simply because they disagree with me, but because a significant influence on where I place Kobe is his poor performance in adjusted +/- statistics (APM).
Oh sure, I can and do mention the fact that he has played less this year than in previous year, that his efficiency is down from peak, that there was evidence from previous years that the Lakers could be quite good even without Kobe, and that the Lakers’ peak level of performance (which requires Kobe’s peak levels of performance) is far above what the Lakers have achieved this regular season. In the end though, if Kobe had a great APM right now, Kobe’s place on my list would be higher, and many people think it’s crazy for me to take a fringe stat so seriously.
The quote above makes a powerful point that I always try to keep in mind as I use stats. The reality is that all serious basketball watchers come to their use of a particular tool set of stats at least partially based on their own understanding and intuition of the game. Thus on a broad strokes level, we are all arguably guilty of being Lang’s drunken man. This behavior is not an inherent problem as long as it does not extend to fine scale analysis, however it’s quite easy to make that leap because doing so is very tempting and often times quite subtle. Were I to ignore Kobe’s APM, then I truly would be the drunk Lang seeks to condemn for I’d then clearly only be using the stat when it fit with my pre-conceived notions.
Let me clarify the situation with Kobe’s numbers here in a set of preemptive statements to the thoughts I think will come to your mind based partly on the arguments I’ve already seen come my way:
Kobe’s APM isn’t simply weak for an MVP candidate, it is horrendous by any standard. I’m not talking about something minor.
What about APM notoriously having a lot of standard error (essentially, randomness) which requires a huge sample size before you make confident statements with it? The standard error is a quantified number, and it is large, but not large enough to make one consider Kobe’s APM insignificant. I realize that Dave Berri said it did indeed make the APM insignificant, but that was in comparing Kobe’s numbers here to average players which isn’t a very useful question to ask. We’re talking about the MVP, let’s compare him to their APM’s according to basketballvalue.com:
As you can see, even when you give Kobe every shred of the benefit of the doubt that standard error provides, he still lags behind the major MVP candidates. (Of course, standard error isn’t any perfect thing either, but for anyone saying that the gap here isn’t significant, c’mon now)
Now I’ve actually got some people telling me that the mere fact that Kobe’s doing so poorly by this metric this year means we need to toss the stat out entirely. Literally, if he had mediocre numbers that would be defensible and thus perhaps usable, but with the level of discrepancy so strong, that tears it, APM is no longer welcome at the party. I’ve had people say this simply because Kobe is Kobe, and Kobe is known to be great. I’ve had people say that because Kobe’s done great in this stat basically his whole prime and that somehow calls into question this year’s result.
All of these are arguments for letting one anecdote completely over turn my previous thinking, despite the fact that there actually are reasons to believe that Kobe’s having significantly less impact than in previous season. I don’t see any reason to change my previously established thinking though. The numbers are what they are, and having such a massive discrepancy essentially kills the low sample size argument. What makes the stat look ridiculous to others, is precisely what makes it impossible to ignore for me.
How I apply adjusted +/- to evaluate Kobe Bryant’s MVP candidacy
This however, does not mean that I need to rank Kobe Bryant as one of the least valuable players in the league because of what this stat says at the most superficial level. As with so much of analysis, whether it be statistical in nature or not, nuanced thinking is required. So let me explain how I interpret these stats into relation to Kobe’s season, and why I rank Kobe as I do.
People tend to have confusion about exactly what APM says, and actually I’d argue, they tend to have confusion about what all stats say. They like to think a stat says which players are better and which are worse. However, all stats come from the 5-on-5 basketball the NBA plays, and are thus influenced by the context in which they were achieved. With +/- statistics this distinction becomes much more pronounced.
Consider a tweener role player whose set of strengths and weaknesses can be exploited by certain types of opposing players but not others. If his coach only puts him in in situations where such opposing players are off the floor, either because the opposing team has no such players, or those players are on the bench, then the tweener the team may end up doing very well with him on the floor.
We’ve seen times in the past where a player who plays role player minutes has an APM among the league leaders, which makes a tweener interpretation like I’ve presented plausible. Does that damn APM as a stat? Well, depends on how you look at things, let me put it another way: Does that mean that APM is meaningless? Here the answer is a resounding “No”. There is meaning, it’s just a question of whether people will grasp the meaning.
Let’s go back to Kobe. People tend to look at his negative APM right now and think that it’s implying that Kobe’s going out there and scoring points for the opposite team, which makes the stat awfully hard to swallow. In reality, when Kobe is on the court, the Lakers are typically beating their opponents by a good amount, the poor APM comes simply because the team is doing so unexpectedly well with Kobe off the court. For Kobe on the floor then, there’s nothing glaring about the team performance that shouts “this isn’t working”. To put it another way: If the goal of the game was to beat your teammates’ performance by as much as possible, and the scoreboard was showing Kobe was routinely underperforming relative to stars on other teams, then these numbers would mean something very different to Kobe than they currently do, and I don’t really have any doubt that he’d find a way to kick up his intensity. That’s not the goal though, the goal is to play well enough to earn a high seed, and if you’re an aging superstar, conserve enough energy so that you have a full tank come playoff time.
So how should one look at the current numbers? Well, I look at it from a supporting cast perspective. In an MVP race, players do get judged implicitly and sometimes explicitly based on how good their supporting cast, otherwise we’d always give the award to the top player on the top team. And hence, Manu Ginobili, the current star of the San Antonio Spurs, is not in many people’s top 5 MVP ballot.
The players ranked ahead of Ginobili then are considered to only be on teams with inferior supporting casts compared to what Ginobili has. The salient question about Kobe’s candidacy becomes: How can one move Kobe Bryant ahead of a star on a team with a superior record, when his supporting cast is so strong that they actually give him a terrible APM – something I don’t believe we’ve never seen in the half dozen years we’ve had this type of advanced stat?
And my current answer is: I can’t. This isn’t a reflection Kobe’s capabilities, but simply based on what we’ve seen this season, Kobe’s got a supporting cast as solid as anyone else, and yet there are teams with better records. That puts a ceiling on how much credit I can give him in the MVP race.
Now last, all of this probably begs the question in the minds of some: “Okay, I get that given what you already believe about +/- statistics, your reasoning about Kobe Bryant follows, but how did you get sold on +/- statistics to begin with?” Very reasonable question, for another post. In the next week, or maybe two, I’ll write more on why I feel it’s necessary to use these stat, and how I do, and do not, use them.
- Derrick Rose, the MVP race, and the Isiah-Iverson Team Model (asubstituteforwar.wordpress.com)