What does field goal percentage actually tell us?
Two of the most important variables that affect FG percentage are 1) who is taking the shot, and 2) where they are shooting from. Field goal percentage is a useful metric for summarizing the probability of a field goal attempt resulting in a made basket, but when the effect of space is overlooked, it is not a valid proxy for shooting ability; in fact, it is often a misleading indicator of how well a player actually shoots. For example, Tyson Chandler led the NBA in overall FG percentage this season. Nearly 68 percent of his field goal attempts resulted in made baskets, which sounds impressive. However, a whopping 96 percent of those attempts occurred within seven feet of the rim. He shot a dismal 2 for 14 from beyond seven feet; his "shooting" abilities are spatially limited.
This is common sense, yet to this point very little analytics work has evaluated the effect of space on shooting percentages. Sure, we consider crude areas like "three-point land" and "in the paint," but as anyone who has ever watched a player clang 20-footer after 20-footer knows, shooting ability varies on much finer scales than that.
With that in mind, I divided the court into eight three-point zones, eight midrange zones, and one close range zone; here are the league leaders in field goal percentage from within each of these 17 zones:
Close to the basket
In the area immediately around the basket, Dante Cunningham of the Grizzlies has the highest FG percentage in the NBA. Cunningham made an incredible 74 percent of his 126 field goal attempts in this area, edging out some slightly less obscure guys, LeBron James (72 percent) and Tyson Chandler (71 percent). As a "role player," Cunningham's ability to score at such a high efficiency here legitimately puts him in an elite group of scorers. For comparison, Ricky Rubio is the league's least efficient shooter in this area, shooting at 41 percent.
In the midrange
About 37 percent of the league's field goal attempts occur within midrange areas. Collectively, this is the NBA's least efficient shooting domain; the league shoots 38 percent from these zones, compared to 55.4 percent from close to the basket and 34.8 percent from the more-valuable three-point land. Players who can score efficiently in these areas are especially valuable. With that in mind, it's not surprising to see that many of the best midrange shooters in the league are among the league's highest paid players. Few of us should be surprised to see Dirk, Nash, Bosh, LeBron or Kevin Garnett in these areas. On the other hand, almost everyone should be shocked to see Rajon Rondo in their company. He's widely known as a woeful jump shooter, and that's not an unfair assessment overall. But Rondo has a few sweet spots from which he is surprisingly effective, and as you can see in his bleak shot chart below, the area off the right elbow is one of those oases. In this area Rondo shot 56 percent, edging out Ty Lawson and Dirk, each at 53 percent.
Beyond the arc, seven different players are represented, suggesting that even the NBA's best pure shooters have unique spatial strengths and weaknesses. The corner three-point shot is the most effective shot in the NBA; it is slightly closer to the basket than other three-point shots, which makes it slightly easier to make. Ray Allen loves the corner three, though he is more effective on his left (graphic right). Allen averaged 1.71 points per attempt from this spot, which was the single most potent player/spot combination in the NBA. In fact, his field goal percentage from there was better than Blake Griffin's free throw shooting-57 percent to 52 percent. From the other corner, the Griffin's teammate Nick Young averaged 1.7 points per attempt, good enough for the second most potent player/spot combination in the NBA this year.
Although Steve Novak led the NBA with an incredible 47 percent from three, he's only the best shooter in the NBA from one small area on his right side. He's great everywhere, but he is only the best of the best in one place.
Kirk Goldsberry examines the NBA using spatial and visual analytics. He publishes some of his work at courtvisionanalytics.com, and you can follow him on Twitter at @kirkgoldsberry. Matt Adams is a spatial analyst living in New York City, who helped out on this study.