One of the more insightful advanced NBA metrics is Box Plus/Minus (BPM).
Box Plus/Minus provides a snapshot of a player’s performance relative to the league average, measured per 100 possessions.
What is Box Plus/Minus (BPM)?
Box Plus/Minus (BPM) is an advanced basketball stat that measures a player’s contribution to the team while on the court in terms of the point differential per 100 possessions.
BPM evaluates a player’s performance in relation to the league average, set at 0.0.
This means a player with a BPM of +5.0 would make his team 5 points per 100 possessions better than a league-average player would.
BPM combines offensive and defensive metrics to give a complete picture of player effectiveness.
The Formulas for BPM
BPM is calculated using a player’s box score information and team context.
The formula has evolved to include more precise adjustments for role and playing context, culminating in two components: Offensive Box Plus/Minus (OBPM) and Defensive Box Plus/Minus (DBPM).
Offensive Box Plus/Minus (OBPM):
OBPM estimates the impact a player has on his team’s offensive performance per 100 possessions, compared to the league average.
The formula incorporates various factors, including points produced, assists, turnovers, and usage rate.
Defensive Box Plus/Minus (DBPM):
Much the same, DBPM measures a player’s defensive impact per 100 possessions.
It considers defensive rebounds, blocks, steals, personal fouls, and defensive plays not captured in traditional metrics.
The combined formula for BPM, integrating both offensive and defensive components, is not publicly detailed as it involves a regression analysis that predicts team performance based on individual player stats.
However, the basic concept is to add OBPM and DBPM:
BPM = OBPM + DBPM
Example of BPM in Use
Consider a hypothetical NBA player, John Doe, who has the following per-game statistics in a season where he plays 75 games, averaging 35 minutes per game:
John Doe – 75 Games – 35 mpg:
- Points: 25.0
- Assists: 7.0
- Rebounds: 8.0
- Steals: 1.5
- Blocks: 0.5
- Turnovers: 3.0
- FGA: 18.0
- FTA: 7.0
Suppose further that his team’s stats per 100 possessions with him on the floor are much better than when he’s off.
After running through the BPM calculation, let’s assume John Doe has an OBPM of +3.5 and a DBPM of +2.0.
Therefore, John Doe’s BPM would be:
BPM = 3.5 + 2.0 = +5.5
This indicates that John Doe makes his team +5.5 points per 100 possessions better than a league-average player would.
History of BPM
Box Plus/Minus was developed by Daniel Myers and first introduced to the public through basketball-reference.com.
Myers aimed to build a solid metric that could capture a player’s overall impact on the game, given the lack of defensive statistics in traditional box scores.
The initial version of BPM was based on regression analysis using historical player data to estimate how changes in player statistics related to changes in team performance.
Over the years, BPM has been refined to better account for the various roles players might have and the different contexts in which they play.
The introduction of BPM 2.0, for example, incorporated more play-by-play data and tracking information to enhance its accuracy, particularly on the defensive side.
Box Plus/Minus – You’ll Hear It Said Often
Box Plus/Minus is a powerful tool in the arsenal of NBA analytics, providing a snapshot of a player’s overall impact on the game relative to the league average.
By quantifying how much better or worse a team performs with a particular player on the court, BPM offers valuable insights for coaches, analysts, and fans alike.
As basketball continues to evolve with a greater emphasis on data and analytics, metrics like BPM will remain essential for understanding player contributions in a detailed and nuanced way.
Check out some more advanced NBA metrics like Usage Rate and True Shooting Percentage.
