Four Factor Fest
Let's dig deep and get nerdy into one of the league's fundamental stats
It doesn’t seem to be talked about much, but a very common set of stats called the Four Factors can be found on most sites which provide a wide breadth of NBA-related statistics. Basically, it seems like it was found that four factors provided enough context on both offense and defense to understand the quality and strategy of a team. The Four Factors are:
Effective Field Goal %
Turnover %
Offensive Rebound %
Free Throw Rate
These are used both in the context of their offense but also their opponents’ offense when they’re playing them (in other words, on defense, they are the eFG% they allow, the turnover percentage they cause, the offensive rebounding they allow, and the free throw rate that they cause through fouls).
Let’s dive deeper than just saying their names, then see what the league looks like with regards to these.
The Factors
Effective Field Goal %
Effective Field Goal % is a composite stat where the percentages are weighed by the points that the shot is worth (not including free throws). Luckily for us, basketball only has two non-free throw shot values: two and three. The formula for eFG%, as many of you know, is:
Currently, the Cleveland Cavaliers are shooting a blistering 59.8% from 2 and 41.6% from 3, and it results in them having an excellent eFG% over 60% (and this number itself may mean nothing to you, but the last place team in the league, Portland, is at 49.8%, for context).
Turnover %
A much more explanatory stat, this just indicates how many possessions for the team with the ball in a turnover. Famously, Chris Paul teams have always been very low on this stat, whereas Steph Curry teams have often been a lot higher here with their high-risk play style (obviously, this is why we have four factors and not just one, because we know who has the rings between those two). But also, on defense, it has to do with how hawkish you decide to be as opposed to being conservative. In their heyday, the Bud Bucks and the Nurse Raptors were on opposite sides here, with the Bucks playing much more conservatively and the Raptors trying to steal every ball possible.
Concerns over turnovers have also influenced the amount of passing teams do, like the Snyder Jazz explicitly deciding to just shoot instead of pass so much, since this would result in less turnovers.
Offensive Rebound %
Offensive rebounding has always had known value, but in recent years, certain teams are shamelessly risking their transition defense in order to decimate opponents on the glass. The Grizzlies are most known for this in recent years, especially because it hasn’t been as easy to sustain in the focused playoff environment.
On defense, it’s simple - rebound the ball. It’s safe to think that rebounding is more hard to plan on because of the fact that teams are playing more guards than in decades past for shooting purposes. It would be safe to think that because this is a safe space, but you’d be wrong. In 2004-05, the median team had an ORB% of 28.7, and in the league today, it’s down to 24.1.1 The fact that it’s more rare likely makes it a more effective regular season weapon in this day and age.
Free Throw Rate
Simply put, this is how many free throws a team makes per 100 possessions. Foul shots are one of the most disliked but important parts of the game, a punishment for bad defense that certain stars like to use to their advantage. Fascinatingly, a certain purple and gold team is always at the top of this, despite what your Hollywood friends may say.
The League
Obviously, there are more factors to winning than these, but they can be extremely informative. My preferred site for this is Cleaning The Glass (which provides other filters which provide even more insight, and nice color coding which is more friendly to my slight colorblindness).
First, I wanted to see which stats correlate most with success on offense or defense2. I took the correlation coefficient for each on offense and defense with their respective rating (Pts/Poss), and got the following (reminder that the closer it is to 1 or -1, the stronger the correlation is for the dataset):
Offense
eFG%: .775
TOV%: .696
ORB%: -.061
FT Rate: .044
Defense
eFG%: .809
TOV%: .679
ORB%: .279
FT Rate: -.001
I would propose that these correlations are more intentional than surprising to teams. On offense, there are few teams that are figuring out how to have effective offenses without making shots (the Rockets are the only team in the bottom half of the league in eFG% but with a top 10 offense). Teams are shooting 3’s at the highest rate ever, and those are often on easier swing passes that are less likely to be turned over.
On defense, surprisingly SEVEN of the top ten on defense are in the bottom half for opponent free throw rate. Most of those teams are high in opponent TOV%, which means that aggressiveness is the trend on defense these days.
NOTE: When you hear a basketball person talk about “winning the possession battle”, they are talking about trying to make sure that you take more shots than the other team. This is why offensive rebounds and turnovers are so important, since those impact the turnover battle. I like to compare the FGA for each team after a game to see how it turned out, because some teams will lose in FG% but win handily because they took 15 more shots over the course of the game.
Some Lineup Four Factors Feng Shui
Cleaning the Glass (is this post just turning into a CtG endorsement?) has a tab for lineups (for specific teams and for the whole league) which uses the four factors as well to see which specific lineups do best.
Looking at the lineups that have played at least 200 possessions together so far, we can see that a few signals among the “small sample size” noise. Houston is clearly focused on an identity (“who cares if we make shots, we’ll just make sure that we make as many as possible”). The Hawks have one man, the Great Barrier Thief, in Dyson Daniels who is taking care of all the turnover forcing necessary. Then Milwaukee, with Giannis, needs to figure out how to get a few offensive rebounds. Either that, or they need to make a lot more shots.
Conclusion
Exploring the four factors has become a favorite past time of mine, and, while it’s not an official endorsement of this website (these stats can be found on basketball reference and the NBA’s website as well). Go and check it out for yourself.
I thought it would be up from before, but I assume that post moves and bigs on the block has a lot to do with this. With bigs farther from the basket than ever, it makes it harder to teams to effectively rebound on offense.
Obviously, there is also strong correlation between having a good offense and defense because of the fact that the very best (and worst) teams have talent advantages or disadvantages. As we can see, the Jazz, Pelicans, and Wizards are probably bad at both because of their roster issues, not because of strategy necessarily.