Nylon Calculus 101: Basic Shooting Adjustments
By Ian Levy
Basic Shooting Adjustments
Effective Field Goal Percentage
Simple field goal percentage is nothing more than a ratio of shots made to shots missed. It would be a perfect representation of shooting efficiency except that not all shots are worth the same number of points. Three-pointers are made at a lower rate than shots around the basket because of the added distance but, in the aggregate, they can provide a similar value. For example, making six out of ten layups provides the same 12 points as shooting four out of ten on three-pointers. Players who shoot a lot of three-pointers often have a lower field goal percentage than players who shoot mostly around the basket, but the result is a comparable level of offensive efficiency.
Effective field goal percentage is meant to remedy this problem by accounting for the extra point earned by a three-point basket. It does this by counting three-pointers as one-and-a-half made baskets in the same ratio of makes to misses. The one-and-a-half piece comes because three points is literally one-and-a-half times two points.
While effective field goal percentage gives a more complete picture of how much offense a player is generating when they shoot, where that offense is coming from is not immediately apparent. You can have two players with identical effective field goal percentages that are achieved in different ways—around the basket or from the perimeter. Pairing a player’s effective field goal percentage with other statistics that describe their offensive role can really help reveal what they are doing on offense and how effective they are at it.
True Shooting Percentage
True shooting percentage takes things one step further by incorporating free throws made and attempted as well. The formula here boils down to points scored divided by true shot attempts (shots and trips to the free throw line) and then is divided in half to create a shooting percentage.
True shooting percentage gives you an idea of how productive a player or team is on all possessions where they actually attempt a shot or draw a shooting foul, essentially all possessions that don’t end in turnovers. Like effective field goal percentage, one caveat is that it is not immediately apparent where the offensive efficiency is coming from. A great jump shooter can have the same true shooting percentage as a big man who never shoots anything but layups and dunks. Pairing true shooting percentage with other descriptive statistics increases it’s explanatory power.
Shooting Stats by Location
The last common adjustment to shooting statistics is to look at some of the categories we’ve already discussed, but by location. Several statistical websites now feature shot charts and tables that let you see a player’s field goals made, attempted, field goal percentage and effective percentage separated by location. This can come in the form of an exact distance from the basket, bins of distance (0-5 feet, 5-10 feet, etc.) or in areas (Restricted Area, Mid-Range, Corner 3, etc.). Being able to parse shooting statistics by location helps inform exactly what a player’s offensive role is or what a team’s offensive structure looks like and adds a lot of context to standalone shooting statistics.