The Four Factors of Basketball
Why does this matter? Read on...
Terrence Vaccaro/NBAE/Getty Images
Dean Oliver, who wrote “Basketball On Paper” and is a statistical consultant for the Seattle Supersonics, has broken the game down into four key factors that determine who wins and who loses:
Merely looking at commonly reported statistics in these areas doesn’t help much in comparing teams. That’s because most of these stats are either out of date (field goal percentage — more on this later) or fail to account for the reality that some teams play faster and some teams play slower.
More meaningful analysis is possible by examining a team’s performance per possession. Dean Smith, the great North Carolina coach, decades ago defined “possession” as the time from when team has the ball until the other team gets it back. Teams take turns with the ball until time runs out, and possessions are approximately equal in a single game.
Possessions: .96 x (field goal attempts + .44 x free throw attempts + turnovers - offensive rebounds).
It’s possible for several “plays” or events to occur on a single possession. A team could miss a shot, rebound the miss, then commit a turnover. It could miss, get the rebound, and get fouled. And so on — as many variations as the players can muster.
Analyzing what a team does per possession (or, per 100 possessions) removes the effect of pace and allows for focus on efficiency — the team that makes best use of its possessions is the team that will win. But what difference does per game vs. per possession data make?
Consider — the Washington Wizards (99.6) rank fifth in points per game this season, while the Milwaukee Bucks (99.4) rank sixth. But, the Wizards have averaged about 90 possessions per game while the Bucks have averaged 93.5. This shows that the Wizards and Bucks are scoring about the same number of points, but that the Wizards are doing it with fewer possessions. So, the Wizards have a good offensive rating of 110.4 points per 100 possessions (6th best in the league), while the Bucks offense is a below average 105.6.
The same analysis works on the defensive end as well. The Wizards (95.0) and Lakers (95.1) are 16th and 17th respectively in points per game allowed. But, it’s taking opposing offenses 2.5 additional possessions to get those points against the Lakers. That means the Lakers have the league’s sixth best defense (102.9 points allowed per 100 possessions), while the Wizards are about average (105.7).
Let’s take a closer look at the four factors that comprise offensive and defensive ratings and define who wins and who loses in the NBA.