Dean Oliver’s book, Basketball on Paper: Rules and Tools for Performance Analysis, was first published in November 2003. Even in its earliest reviews, it was hailed by Kevin Pelton as “a revolutionary strike for statistical analysis of the game of basketball.” It was here that many basketball fans were exposed to Dean Oliver’s "Four Factors of Basketball Success" for the first time. Winning basketball games can, according to Oliver, be broken down to the simple concept:
“A team that has a higher offensive rating (points scored per 100 possessions) than defensive rating (points allowed per 100 possessions) wins the game.”
Oliver took this concept one step further by breaking these ratings down into four elements: shooting, turnovers, rebounding and getting to the foul line. If you can control these four aspects, your team stands a good chance of winning any individual game and is more likely to have success throughout the season. However, not all factors are created equal, and Oliver has assigned weights to each factor to reflect this. [note: Oliver’s weights are based on a 1-10 scale, with 10 being the most strong predicator for winning games and 1 being the least]
(1) Shooting Percentage  40%
(2) Turnovers per Possession [5-6] 25%
(3) Offensive Rebounding Percentage [4-5] 20%
(4) Getting to the Foul Line [2-3] 15%
These factors can be applied to both the offensive and defensive side of the ball, giving us eight factors instead of four. Obviously on the defensive side the goals are reversed. For example, on defense you would want to limit your opponent’s offensive rebounds, thereby reducing their offensive rebound rate. Let’s take a look a closer look at each factor.
The shooting factor is measured using Effective Field Goal Percentage or eFG%, which takes in account that a three point field goal is worth one more point than a two point field goal. The exact formula for eFG% is given as:
Shooting the ball well is the most important of the four factors. If a team is struggling in this category, it had better be performing exceptionally well in the other three areas. The importance of this factor cannot be understated. Take a look at the chart below of the top 10 teams based on eFG%.
For the most part, we can see that the teams with the top eFG% ratings are generally more successful at winning games. However, many will be quick to note that teams like the Indiana Pacers, Portland Trail Blazers, Memphis Grizzlies and Chicago Bulls are absent from this list, despite their impressive records. "Four Factor logic dictates that since these teams are not elite shooting teams they must be performing well in the other areas to make up for it. We will examine these teams and the outlier that is the Atlanta Hawks more closely later on.
Turnovers per Possession
Turnovers are important because a team cannot shoot, let alone score, if it commits a turnover. That being said it is important to adjust the number of turnovers a team commits to the pace at which it plays. More possessions are more likely to lead to a higher number of raw turnovers committed. In fact, this is true of all four factors, as the calculations are effectively percentages of some total.
A possession in basketball effectively ends when the ball changes hands. This change may occur via a made shot, a defensive rebound or a turnover. Therefore, the formula for Turnovers per Possession is:
NBA.com takes a similar approach but multiplies this number by 100 to determine a TO Ratio. TO Ratio is simply defined as “the number of turnovers a team averages per 100 of its own possessions.” That being said, let’s take a look at how our eFG% leaders rank in terms of TO Ratio.
Offensive Rebound Percentage
If a team can get back its missed shots at an above-average rate, it can somewhat make up for any deficiencies it has in terms of pure shooting ability. The team does need to score at some point but, as Oliver puts it, giving your team multiple opportunities gives it a chance to win even if your gunners from the outside are missing. Offensive rebound percentage can be derived by dividing the team’s offensive rebounds by the number of opportunities it had to obtain offensive rebounds.
Bringing us back to our study, the chart below dictates how our ten teams measure up in terms of their ability to grab offensive rebounds and generate second chance opportunities on offense.
Getting to the Foul Line
Oliver has written that he specifically phrased this as “getting to the foul line” instead of “making foul shots” or “free throw percentage” or “free throws,” because he determined that the most important aspect was actually attempting foul shots. He goes on to say that teams that get to the foul line more often are more effective than teams that make a high percentage of their foul shots. There are exceptions on an individual game basis but, by and large, Oliver has found that “getting to the line more frequently wins a lot more games than missing a few freebies will lose.”
That being said, the formula for calculating this factor is known as Free Throw Attempt Rate. FTAR is defined as the number of free throws a team shoots in comparison to the number of shots the team shoots.
Oliver had said that these four factors were essential to winning basketball games. However, as we dive deeper and deeper into this analysis, we can see that there is no one right way to build a team. If your team struggles in one factor area, it can make up for it by being particularly good in others.
As mentioned previously, there is no one way to build a team. However, Oliver’s four factors allow us to see which teams are able to control the key aspects of winning basketball games. You can be poor in one area and make up for it in others. For example, the chart below shows that the Chicago Bulls are not a very productive team when analyzed by the four factors on offense as a whole. However, they are exceptional at generating additional opportunities on the offensive end, and their strong ability to limit their opponents' four factor success on the defensive end has allowed them to put together a strong season despite losing their most prolific player.
These rankings were based team performance prior to games played on 4/1/14. As Oliver made note of, there is one strong theme amongst the top teams in the NBA. Most of them are exceptional in terms of eFG% and limiting their opponent’s eFG%, allowing them to control what Oliver has deemed to be the most important aspect of winning basketball games.