The Shooting Terrain of the NBA: Mapping Field Goal PercentageMar 20
Some shots are easier than other shots; that’s a basic tenet of basketball. Many factors influence the probability of a field goal attempt resulting in a made basket, but one factor in particular has been mostly overlooked in basketball analysis: location. The most common shooting metric in the NBA is field goal percentage, which measures the percentage of field goal attempts that result in made baskets. Usually this metric is applied in a non-spatial way to describe how effective a given player or team is at “putting the biscuit in the basket.” However, despite its ubiquity in all levels of basketball analysis, very few people have ever sought to measure and/or visualize the spatial dimensions of FG%.
The following graphic visualizes FG% in the NBA this season; it demonstrates that some shots are easier than others, and quantifies this effect. As you can see, some fascinating insights begin to emerge:
The first thing I notice is the extremely steep slope near the basket. This indicates that the likelihood of a shot going in rapidly decreases within a short distance of the hoop. League-wide, the highest percentage field goal attempts occur very close to the basket (consider that your dumb CourtVision revelation of the day); however, collectively the league shoots just over 60% near the basket. This number seems low until you consider the frequency of missed tip-ins, blocked shots, contested lay-ups etc. Regardless, within a span of about 8 feet in any direction FG% decreases drastically, down to 43%. Further, with a few exceptions, a vast majority of the court space is in sub-40% territory; in fact, about half of shot locations are somewhere between 35 and 40%, but since a disproportionate amount of shots occur near the rim, this does not mean that the average nba shot is below 40%.
Another interesting artifact is the 42% area around the free throw line; it’s clearly the most efficient 15-16 foot shot on the court. From other directions, a shot of this distance may only be a 37% shot. Players are more effective in front of the hoop; the shape of the 40% contour demonstrates that. The larger point is that all shooting directions are not equal. There are several reasons for this, but the spacing of defenders is clearly one of them.
One obvious thing to consider here is that this is a composite map that does not apply to individual players. One of the main points of my project is to reveal the unique spatial tendencies of every player, line-up, and team in the league. This graphic does not do that, but it does enable the ability to measure individual players or defenses against a spatially-informed league average. Stay tuned for that.
The End. Thanks to Jumpin’ Matt Adams.