True Shooting percentage is a popular statistic roughly designed to capture points per shot. But since it mashes together 2-point field goals, 3-point field goals and free throws, the final percentage isn’t exactly intuitive. What does it mean to have a TS% of 55% versus one of 60%? Precisely, how much more efficient is that?
Let’s look at three different types of players: low-usage, medium-usage and high-usage, defined as
- low-usage players take roughly 10 attempts per 75 possessions (FGA’s + FTA’s*0.44)
- medium-usage players take roughly 15 attempts per 75 possessions
- high-usage players take roughly 20 attempts per 75 possessions
Current examples: Shane Battier is low-usage, averaging 9.4 attempts per 75, Kevin Garnett is a medium-usage player, averaging 16.2 attempts per 75 and Dirk Nowitzki is high-usage, averaging 21.3 attempts per 75. Kobe Bryant is the league-leader right now, at just over 27 attempts per 75 possessions.
So, what is the relationship between TS% at these rates and actual scoring efficiency? Well, the more a player shoots the more the percentage points matter. By definition, there is a simple linear relationship between TS% and points, shown below graphically:
So for someone like Battier, every one percent change is worth about 0.2 points. For Garnett, about 0.3 points and for a high-usage guy like Nowitzki, every single percent change is worth about 0.4 points. So, returning to the idea of low, medium and high-usage players, we can look at their affect on a team’s Offensive Rating. For every one percent change in TS:
- low-usage players change an ORtg by 0.2 points
- medium-usage players change an ORtg by 0.3 points
- high-usage players change an ORtg by 0.4 points
That means when comparing high-usage stars, a small change in TS%, say 2%, roughly equates to almost 1.0 point in offensive efficiency. This is not inconsequential, as that approximates to an SRS point, usually good for a handful wins in a season. A 4% change is worth about 1.5 points in ORtg, and a 6% difference 2.5 points or nearly 3 SRS points. A change of that magnitude in SRS is often the difference between an average team and a solid playoff team, or a solid playoff team and a title contender.
In other words, the 5.9 % TS difference between LeBron James in 2010 (24.8 “attempts” per 75) and Kobe Bryant in 2010 (24.7 “attempts” per 75) is worth about 2.9 points, based on their shooting efficiency.
Keep that in mind when comparing TS% numbers. For a better look at estimating overall “offensive efficiency” as it changes with usage see this post at Basketball-Reference.