David Berri on Adjusted Plus/Minus

1 Comment

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. 

Joakim Noah with as ugly a free throw as you’ll see. And he knows it. (VIDEO)

Leave a comment

Joakim Noah used to be a good free throw shooter, he’s hit 70 percent for his career. But he’s shooting just 42.9 percent this season.

And no miss was uglier than the one Monday night against the Pacers.

The best part of this airball was Noah’s reaction — he knew it was bad the second he let it go.

If you want to draw parallels with the Knicks’ season, go for it.

Stephen Curry finds Kevin Durant for tomahawks slam in transition (VIDEO)

Leave a comment

The Warriors in transition can be beautiful basketball.

And if you don’t stop the guy with the ball from getting a straight line to the hoop, there will be highlights. In the first half Monday night, the Heat did a good job making Stephen Curry give up the ball in transition (not letting him just pull up for a three), but he found Kevin Durant, who found a lane to the basket, and… highlight tomahawk dunk.

It was a two-point game at the half between the Heat and Warriors, after what was a second quarter both teams probably want to forget.

Warriors’ Steve Kerr calls some players’ All-Star votes a “mockery”

INDIANAPOLIS, IN - NOVEMBER 21:  Steve Kerr the head coach of the Golden State Warriors watches the action during the game against the Indiana Pacers at Bankers Life Fieldhouse on November 21, 2016 in Indianapolis, Indiana.    NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this photograph, User is consenting to the terms and conditions of the Getty Images License Agreement  (Photo by Andy Lyons/Getty Images)
Leave a comment

MIAMI (AP) — Golden State coach Steve Kerr wishes players had taken their voting for the NBA All-Star Game more seriously, calling it a “mockery” after nearly 300 players in the league wound up on at least one ballot.

Players had a say in deciding starters for next month’s game in New Orleans, with their selections accounting for 25 percent of someone’s total score in the balloting. Fan and media votes were also part of the process of selecting starters, and NBA coaches vote this week for the reserves to be revealed on Thursday.

“I am very disappointed in the players,” Kerr said before the Warriors played the Miami Heat on Monday night. “They’ve asked for a vote and a lot of them just made a mockery of it. I don’t know what the point is.”

Nearly 100 players got only one vote from either themselves or an NBA peer in the All-Star balloting, including Mo Williams – who hasn’t played a single second this season. The NBA said a total of 324 players participated in the voting process.

Kerr was asked why he would use the word “mockery.”

“I saw the list,” Kerr said. “I saw all the guys who got votes. … There were 50 guys on there who had no business getting votes. Although a lot of people wrote in their buddies in the presidential vote as well. So maybe that’s just their own way of making a statement. I think if you’re going to give the players a vote, I think they should take it seriously.”

In past years, starters have been picked entirely by fan vote. This year, those whose All-Star hopes now hinge on the coaches’ vote include Dwyane Wade, Zaza Pachulia, Joel Embiid, two-time All-Star MVP Russell Westbrook and perennial All-Star pick Carmelo Anthony. Wade, Pachulia and Embiid would have started under the old formula.

Kerr said the change to the way starters are picked this year didn’t affect the way he made his votes for reserves. He sent his vote in Sunday.

“Didn’t alter anything,” Kerr said.

Heat coach Erik Spoelstra said he called a staff meeting to get input on the ballot he’ll send to the league.

“How is Russell Westbrook not in the starting lineup?” Spoelstra asked. “I know how it’s important to players and especially guys that are giving their heart and soul and emotions into the game and should be rewarded for it. I do have to admit, in some years past, I would just give it to my assistants. Not anymore.”

Spoelstra said he told Heat center Hassan Whiteside, another All-Star reserve hopeful, that to be picked as an All-Star backup wouldn’t be a consolation prize but rather would be a sign of respect.

“Players, they’re not all voting. Fans, you have no idea where that’s coming from,” Spoelstra said. “But coaches … they’re paid to figure out who helps teams win and I think that’s the ultimate compliment if you get voted in by coaches. So I’m taking that responsibility a lot more seriously than I have in the past.”

Timberwolves purchase Iowa Energy D-League team

Fort Wayne Mad Ants v Santa Cruz Warriors - 2015 D-League Finals Game Two
2 Comments

MINNEAPOLIS (AP) The Minnesota Timberwolves have purchased the Iowa Energy and will begin a direct affiliation with the NBA Development League team next season.

The Timberwolves announced the agreement on Monday. Owner Glen Taylor is purchasing the team, which previously had a hybrid partnership with the Memphis Grizzlies. The Wolves will become the 18th NBA team to have a direct affiliation with a D-League team.

It’s a growing trend across the league for franchises to use the minor league teams to help develop young players, coaches and executives and help players rehab injuries.

The Timberwolves were looking for a team close to the Twin Cities to allow for easy back-and-forth travel. Energy owner Jed Kaplan will remain with the team and partner with Taylor.