Monday, January 11, 2016

The NBA Metrics


When comparing basketball players across time periods two key variables need to be accounted for:

  1. Pace of the game (which strongly influences total shot attempts)
  2. Shooting efficiency of the league as a whole 

In any basketball game a valuable scorer is one who is unique.  This means they are outperforming their peers at an elite level.  Stephen Curry today is a better shooter than Jerry West was in 1965 but how valuable is Curry compared to the average NBA guard in 2016?  How great a scorer was West contrasted with his competition back in '65?


NBA Metrics for all of Pro Basketball History 

  • Points Above Average

Measures scoring production compared to the average player in each season of NBA history.  To calculate Points Above Average start with the players shot attempts, then multiply by the league average points scored per shot attempt.  Finally subtract that number from the actual points scored by the player.

In math terms it looks like this: 

POINTS ABOVE AVERAGE = PLAYERS POINTS - TRUE SHOT ATTEMPTS x LEAGUE AVERAGE POINTS/TRUE SHOT ATTEMPT

True Shot Attempts is an estimate of the total number of shots each player has used including free throws (every two free throw attempts counts as almost one 'True Shot').  The formula for TSA is 

Field Goal Attempts + 0.44 x Free Throw Attempts 


  • True Shooting Plus

Measures shooting efficiency compared to the average NBA player in each season of league history.  Appears on NBA Metrics as "True Shooting+".

In math terms:

TRUE SHOOTING+ = (PLAYERS POINTS PER TRUE SHOT ATTEMPT / LEAGUE AVERAGE POINTS PER TRUE SHOT ATTEMPT)*100


Example using Stephen Curry in 2015

Points - 1900
True Shot Attempts - 1489 (1341 Field Goal Attempts + 0.44*337 Free Throw Attempts)
Points/TSA - 1.276
NBA Average Points/TSA - 1.068



1900 Points - 1489 True Shot Attempts * 1.068 NBA Average Points/True Shot Attempt = 309 Points Above Average 


(1.276 Points per TSA / 1.068 NBA Average Points per TSA) * 100 = 119 True Shooting Plus

This means Curry's shooting efficiency was 19% higher than league average.  Or each given 100 shots, Curry scored 119 points while the average NBA player scored 100.