Advanced Stats: eFG%

The Numbers

Every relationship needs balance. In the hot moment, there is red, orange, blue, yellow fire. Most of the rest of the time, there is discussion, dialogue, thought. Without one, the other lulls. Together, there is harmony.

Basketball games, the best ones, are emotive affairs. They leave you light-headed and breezy (that comeback home win against the Heat last season), they leave you inspired and perplexed (that game last season when Monta Ellis scored 16 straight points in the fourth quarter), they leave you dazed and sunken (that Derrick Rose last-second game-winner last season).

But for those of us who really throw our heart into this, the basketball games leave us discussing, evaluating, and contemplating long after the game on the court ends. We think about not just what happened, but why it happened – to attempt to make some sort of sense of all the madness, all the happiness.

That is why statistics enhance my basketball experience. And why advanced statistics advance it.

This, the first in a four-part advanced stat series covering what are sometimes referred to as the Four Factors, covers eFG%. The Four Factors are valuable considered individually, but most educational when considered together.

The Stat
eFG% stands for Effective Field Goal Percentage. The statistic accounts for the fact that a three-point field goal is worth more than a two-point field goal, as described by basketball-reference. The formula is (FGM + 0.5 * 3PM) / FGA.

The Old

The conventional statistic to measure shooting efficiency is FG %. This statistic is still valuable, as long as you know exactly what it measures: it simply divides the number of field goals made by the total number of field goal attempts. If Brandon Jennings shoots 9-25 from the field, his FG% for that game is .360. If Jennings makes 7-14 three-pointers in that same game, his FG% for the night is still .360.

The New

Of course, if Jennings makes 7-14 three-pointers in that game, his 3PT% is an impressive .500. But what if wanted to more fairly sum up his shooting efficiency and productivity with one number, rather than two? What if we want to compare his contributions quickly against a player who did not take any three-pointers, or one who did not make any three-pointers?

Enter eFG%. 

After properly weighting for two-pointers and three-pointers, Jennings emerges from that 9-25 shooting game with a .500 eFG%. To put that into perspective, Paul Millsap (.499), Paul Pierce (.499), and Kevin Love (.497) finished 2011-12 with an eFG% right in that range.

Another example: Mike Dunleavy shoots 4-8 but 0-1 on three-pointers, while Carlos Delfino shoots 3-6 but makes 3-5 three-pointers. They both have an equal .500 FG%. But that doesn’t fairly represent their contributions shooting from the field, right? When it comes to eFG%, Dunleavy stays at .500 while Delfino jumps to .750.

All of the aforementioned examples happen to draw directly from the comeback home win against the Heat last season.

The Leaders

As the graph at the top of the page shows, the Spurs led the NBA in eFG% in 2011-12. They also led the NBA in FG% last season, though the margin was much greater for eFG%, since they were the best three-point shooting team as well.

The individual leaders for 2011-12 eFG% provide a nice contrast. Tyson Chandler led the NBA with a .679 eFG%. Chandler also finished with a .679 FG%, having shot 0-2 on three-pointers (fun fact: Chandler is 0-8 in his NBA career on three-pointers). He narrowly edged sharpshooter Steve Novak, who boasted a .675 eFG% last season. Novak managed that despite a relatively modest .478 FG%. But then, Novak also carried an NBA-best .472 3PT%. So, while he did not make nearly the straight percentage of shots that Chandler did, many of the shots he did make were worth more – and that illustrates the essential value of eFG%.

The Offense

The Bucks ranked 17th overall with a .481 eFG% in 2011-12, close to the league average of .485. Mike Dunleavy led the team, at .557.

Looking ahead to the upcoming season, there is some reason to believe that the team can improve its eFG%. Brandon Jennings has upped his eFG% each of his first three seasons. Monta Ellis has a career eFG% better than the one he delivered last season. Ersan Ilyasova and Mike Dunleavy would be fine to simply come close to replicating their fine seasons. Ekpe Udoh can probably only go up from here, Beno Udrih should recover from a relative down shooting season, and Tobias Harris figures to improve his efficiency, as still one of the league’s youngest players. Five of the seven players who played for the Bucks last season that are no longer with the team had eFG%s lower than team average, and incoming rookies John Henson and Doron Lamb should only see much of the court if they are helping, not hurting.

This type of thing is impossible to project, but it would not surprise if the team improved in this area, particularly as there is room for growth. While the offense greatly improved last season, that had more to do with reasons other than shooting efficiency (reasons that will be covered in some of the next parts of this series), as the Bucks remained a positively average shooting team.

The Defense

As always, offense is only half of the story. Also educational is to examine how the Bucks hold opponents in terms of eFG%. And, although the team took a major leap forward offensively and a significant step back defensively last season, when it comes to eFG% the Bucks were roughly the same offensively and defensively. 

The Bucks finished 16th in defensive eFG%, meaning they held opponents to the 18th lowest eFG%, at .489, compared to the league average of .487. Looking ahead to this season, if Samuel Dalembert can maintain his history of good health, the team should be primed to climb at least a few spots.

The Outlook

Just as last season’s offensive mini-explosion was not the result of the team shooting with great accuracy from the field (17th in offensive eFG%), the big downgrade on the defensive end was not simply because the team allowed opponents to shoot such a blistering rate from the field (16th in defensive eFG%).

After all, who really would have thought that the Bucks actually ranked lower shooting (17th) than they did defending shooting (16th) in 2011-12? The real reasons for the offensive success and defensive struggles are not quite as obvious – it is not always as easy as seeing which team makes a better percentage of shots (even when you account fairly for the most valuable ones). This is just part of the explanation.

And that is why this is merely one part of four in a series that could be a thousand stories long – the answers are found in a delicate balance.