Keeping Score: Viewing The NBA Through A Statistical Lens

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Keeping Score: Viewing the N.B.A. Through a Statistical Lens
By JUSTIN KUBATKO  NOVEMBER 11, 2010 6:00 PM
Justin Kubatko is the creator of Basketball-Reference.com, an online basketball encyclopedia. He is also a statistical consultant for the Portland Trail Blazers.


In 1982, the “Bill James Baseball Abstract” was published on a wide scale for the first time, sparking a statistical revolution in baseball. James’s influence, however, was not confined to the diamond. Two young basketball fans, Daryl Morey and Dean Oliver, fascinated by James’s innovations, began to view basketball through a similar lens. Today, the approach of combining traditional scouting with statistical analysis has taken hold in the N.B.A. Morey, who never played competitive basketball beyond high school, is general manager of the Houston Rockets, and Oliver is in the Denver Nuggets’ front office.

This is not to suggest that the two sports are on equal ground when it comes to analysis. Aside from the head start provided by James and many others, baseball has the advantage of being a sport in which the interaction among players is somewhat limited, making it easier to separate an individual’s accomplishments from those of the team.

Basketball is far more fluid and interdependent, making it more difficult to isolate an individual’s true impact on a team. That said, progress on the basketball side has been steady, and while there is much to do, much has been accomplished. This season we will examine the N.B.A. from an analyst’s perspective, and in advance of that we would like to introduce you to some of the statistics you will see on a regular basis.

Simple Rating System is a team ranking that takes into account both point differential and strength of schedule. S.R.S. is denominated in points above or below average, where zero is average. For example, last season the Orlando Magic had an S.R.S. of 7.1, the best regular-season mark in the N.B.A. In other words, we estimate that the Magic was 7.1 points better than an average team.

Win Shares is an estimate of the number of wins contributed by a player. It includes a player’s accomplishments on offense and defense, and takes into account things like playing time, offensive role, shooting efficiency and team defense. LeBron James led the N.B.A. with 18.5 win shares in 2009-10 and 20.3 in 2008-9.



The Spurs’ Dennis Rodman grabbed 29.7 percent of all available rebounds while on the court in the 1994-95 season, the best in N.B.A. records.



Total Rebound Percentage is an estimate of the percentage of available rebounds a player grabbed while he was on the floor. It is an improvement over rebounds per game because it takes into account opportunities, which are influenced by the pace that a team plays and the number of missed shots that a team forces. The best single-season mark since 1970-71 (the first season opponent statistics were officially recorded) belongs to Dennis Rodman in 1994-95. We estimate that Rodman grabbed an amazing 29.7 percent of all available rebounds while he was on the floor that season.

Assist Percentage is an estimate of the percentage of teammate field goals a player assisted while he was on the floor. The playmaking abilities of players who take a lot of shots are often underrated when we focus on a statistic like assists per game. For example, last season Jason Kidd averaged 9.1 assists per game while Dwyane Wade averaged 6.5 assists per game. But Kidd averaged only 3.6 field goals per game compared with 9.3 field goals per game for Wade. When we factor out the shots made by Kidd and Wade, we estimate that both players assisted on 36.4 percent of their teammates’ field goals.

With the help of statistics like these, fans can get a better, more complete view of the players and the teams than they would with a cursory look at the traditional box score. Thanks to the inspiration provided by Bill James, basketball’s statistical revolution is under way.



Basketball Statistics:  A Different Look

(Through Wednesday)

Assist Percentage Leaders for 2010-11 [1]----------Total Rebound Pct. Leaders for 2010-11 [2]

Player---------------Tm-----Ast %-----------------Player----------------Tm-------TRB%

Steve Nash----------PHO----54.7-------------------Kevin Love-----------MIN-------23.3

Rajon Rondo---------BOS----49.5-------------------Kris Humphries--------NJN-------21.8

Chris Paul------------NOH---45.9-------------------Dwight Howard--------ORL-------21.7

Deron Williams--------UTA---43.9-------------------Zach Randolph--------MEM-------21.1

Russell Westbrook-----OKC---43.7-------------------Blake Griffin-----------LAC-------19.5

Jose Calderon---------TOR---42.9-------------------Tyson Chandler--------DAL-------19.3

Devin Harris-----------NJN----42.6-------------------Emeka Okafor---------NOH-------18.7

Derrick Rose-----------CHI----40.5------------------Andrew Bogut----------MIL-------18.6

Baron Davis------------LAC---40.4------------------Tim Duncan------------SAS-------18.5

John Wall--------------WAS---39.4------------------Kevin Garnett----------BOS-------17.9



Simple Rating System Leaders for 2010-11 [3]---------Win Shares Leaders for 2010-11 [4]

Team----------W-----L-----SRS---------------------Player-----------------Tm--------WS

San Antonio----46----9-----7.1----------------------Chris Paul--------------NOH-------11

Miami----------41----15----7------------------------Pau Gasol--------------LAL--------10.2

Boston---------40----14----6.3----------------------LeBron James----------MIA---------10

Chicago--------37----16----5.4----------------------Dwight Howard---------ORL---------9.8

Orlando--------36----21-----5.4----------------------Kevin Love------------MIN---------9.1

Lakers---------38----19-----5.3----------------------Dwyane Wade---------MIA---------8.5

Dallas----------39----16----3.5-----------------------Paul Pierce------------BOS---------7.9

Denver---------32----25----2.4-----------------------Al Horford-------------ATL----------7.9

Oklahoma City--35----19-----2.4----------------------LaMarcus Aldridge-----POR----------7.7

New Orleans----33----25-----2.1----------------------Derrick Rose-----------CHI----------7.7

Memphis--------31----26-----1.4

Philadelphia-----27----29-----1.1

Houston--------26----31-----0.7

Portland--------32----24-----0.6

Knicks----------28----26-----0.3

Atlanta---------34----21-----0.3

Phoenix---------27----26-----0.2

Utah------------31----26-----0.3

Indiana---------24----30------0.4

Milwaukee-------21----34------1.2

Golden State----26----29-------2.1

Clippers---------21----35-------2.7

Charlotte--------24----32-------2.7

Detroit----------21----36--------3.7

Sacramento-----13-----40--------5.2

Toronto---------15-----41--------5.4

Minnesota-------13-----43--------5.5

Nets------------17-----40--------5.9

Washington-----15-----39---------5.9

Cleveland-------10-----46---------10

[1] Assist Percentage; an estimate of the percentage of teammate field goals a player assisted while he was on the floor.
[2] Total Rebound Percentage; an estimate of the percentage of available rebounds a player grabbed while he was on the floor.
[3] Simple Rating System; a team rating that takes into account average point differential and strength of schedule. The rating is denominated in points above/below average, where zero is average.
[4] Win Shares; an estimate of the number of wins contributed by a player.


bob



.

Bob,

Looks like you're ready for a stint at MIT with all your statistical contributions lately. I like the written descriptions of the various measures.

Sam