David Berri on Adjusted Plus/Minus

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Way back in 2006, David Berri, Martin Schmidt, and Stacey Brook came out with a book called The Wages of Wins. It was supposed to be Moneyball for sports other than baseball, but for a lot of people, the book read like Moneyball with a serious chip on its shoulder. In a team game with lots of variables, Berri and his co-authors were confident in their regression-based assertions that  there were 90 players more valuable than Allen Iverson during the season that he won MVP, that scoring was vastly overvalued while rebounding was too often neglected, and Ray Allen had been just as good throughout his career as Kobe Bryant. 

The general feeling among a lot of hard-core basketball fans and analysts was that the Wages of Wins system, which relied only on box-score based statistics, couldn’t possibly accurately capture everything that made a player valuable in a five-on-five game. The logical extreme of that philosophy came in the form of Wayne Winston, the former stat guru for the Dallas Mavericks whose brainchild was adjusted plus/minus, which sought to measure a player’s value without using any box-score statistics whatsoever. As it turned out, he had some even more outlandish conclusions than Berri and co. did. He said that the Knicks should never have traded Tim Thomas, that Lamar Odom was better than Kobe Bryant, and that Kevin Durant wasn’t helping the Thunder win. 
After last weekend’s Sloan stats and analytics conference, David Berri has a short post up on adjusted plus/minus. Here’s the crux of Berri’s argument for box-score bases metrics over adjusted plus/minus:
JC Bradbury and I – in a forthcoming article in the Journal of Sports Economics — report that only 7% of a player’s adjusted plus/minus is explained by what a player did the previous season (oddly enough, unadjusted plus/minus has a stronger – albeit still relatively weak – correlation).  In other words, the correlation coefficient for adjusted plus/minus from season-to-season is below 0.30.   And when we look at players who switch teams – as Songaila did – we fail to find a statistically significant relationship. In contrast, any measure (PERs, Wages of Wins measures, NBA Efficiency, Win Shares, etc…) based on the box score will have a correlation coefficient of at least 0.65, and often these marks are above 0.80. 

Berri makes a solid point. He uses Darius Songalia as a case study for how inconsistent adjusted plus/minus can be, but he could easily have used Kevin Durant, who started the season as a posterchild for how plus/minus based stats could contradict box score metrics but is now an example of how elastic adjusted plus/minus can be from season to season. 

I’m a big believer in using advanced stats to gain knowledge about basketball, but it appears that both Berri and Winston have holes in their metrics. Berri’s box-score based metrics don’t necessarily reflect who was doing what helped his team win the game. For example, let’s say Matt Barnes plays great defense on Kobe for 20 seconds and forces him into a tough fadeaway. Dwight Howard then blocks out Pau Gasol and keeps him from getting to the rebound. The ball caroms off the rim and goes to Vince Carter, who collects the easy rebound. In Berri’s system, only Carter gets credit for doing something right on that play. 
Winston’s system would theoretically give Barnes and Howard most of the credit for the play above. However, the issue is that they could have radically different roles on a different team. With another team, Barnes might not be a starter or a perimeter scorer, but a stretch four who provides energy and outside shooting off the bench without giving much on the defensive end. Thus, he could have a radically different value with a different team. 
Advanced statistics in basketball are wonderful, but they are far from airtight. For the foreseeable future, the best approach with advanced statistics will be to use a number of different metrics and see how they inform each other rather than wait for one perfect formula to reduce contributions to a single integer. 

Spurs to give Tim Duncan, Manu Ginobili Friday night off in Denver

Manu Ginobili, Harrison Barnes, Tim Duncan
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The Spurs are 12-3 and comfortably in second place in the West, they have the best defense in the NBA allowing just 93.8 points per 100 possessions, and they have a top-10 offense to go with it.

So, time to start making sure guys are rested.

That is the first night of a back-to-back, with former Spurs’ assistant coach Mike Budenholzer and his Atlanta Hawks coming to San Antonio on Saturday. Popovich is saving his two veterans for that game.

Duncan and Ginobili have looked like they found the fountain of youth this season. Duncan is taking on less of the offense but has been very efficient in those moments. Ginobili has the impact he did a few years back in his bench role.

What Gregg Popovich cares about is them playing like that come the postseason. So they will rest on Friday.

Brandon Armstrong impersonates Ray Allen (video)

2014 NBA Finals - Game Five
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Ray Allen is retired-ish, but he’ll always be running through screens – in our mind and in this video.

Celtics draft pick Marcus Thornton gets beer dumped on head during Australian game (video)

Marcus Thornton, Will Cherry

The Celtics drafted Marcus Thornton with No. 45 pick in the 2015 NBA draft. That essentially entitled him to the required tender – a one-year contract offer, surely unguaranteed at the minimum.

Thornton rejected that, which is almost always a mistake.

Rejecting the tender is a favor to the drafting team, which gets to keep the player’s exclusive rights for a year. If Thornton tries to join the NBA now, he’s stuck negotiating with only the Celtics.

By accepting the tender, the player typically gets one of two outcomes. He either plays on that contract and draws an NBA salary or he gets waived. But even getting waived is better than rejecting the tender, because at least the player becomes a free agent and can negotiate with any team.

Players who reject the tender go to another league and play for less money. In Thornton’s case, that mean Australia.

How’s that going?

(Almost) never reject the required tender as a second-round pick.

Byron Scott says they just have to get Kobe Bryant better looks

Kobe Bryant, Joe Johnson, Byron Scott

Kobe Bryant is averaging 15.2 points a game at age 37. It’s just taking him 16.4 shots per game to get there. After his 1-of-14 shooting performance against the Warriors the other night — with too much isolation and too many plays run just for him — there has been a lot of talk about his shot. With reason, this is his shot chart so far this season.

Kobe shotchart season

So what do the Lakers’ do? Get Kobe to shoot less and get the ball in the hands of the young stars they supposed to be developing more? Nah.

They just need to get Kobe better looks, Scott told the Los Angeles Times.

“I know his mentality is that he can still play in this league,” Scott said. “And we feel the same way….

“Obviously he’s struggling right now with his shot, and I think everybody can see that,” Scott said. “So it’s trying to get him in better position to be able to have an opportunity to knock those shots down on a consistent basis. That’s No. 1.

“I don’t know if it’s his legs. I don’t think so. Again, our conversations are pretty blunt. … He tells me when he is tired and he tells me when he’s not tired. And the last few days, he said he feels great. So, I don’t think it’s a matter of him being tired or his legs being tired. I think it’s a matter of his timing being a little off.”

Yes, how could it be his legs? It’s not like he’s a 37-year-old with more than 55,000 NBA minutes played, and coming off an Achilles rupture and major knee surgery.

Honestly, I hope the Lakers and Kobe find a balance soon, because they have become just hard to watch. And I don’t want Kobe to go out this way.