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Introduction
Whether it was the notion of "high percentage shots" coined in the early days (which almost exclusively referred to layups and post-ups) or the modern era of pace, space, and emphasis on three-point shooting, basketball teams have always wanted to optimize their players' scoring and ensure that no shot taken is wasted. In order to measure a player's efficiency, teams have traditionally used simple metrics like field goal percentage or looked at isolated quantities such as shots attempted, three-pointers made, or offensive rebounds collected. However, it has only been a few years since people have really started taking a deep dive into creating an all-encompassing metric that accurately quantifies a player's efficiency. Each time a new metric is created, some other factor that was not previously taken into consideration is introduced. In this article, we aim to take the current state of scoring efficiency metrics one step further–by considering actions that are beyond the realm of merely scoring points but still impact a player's overall scoring efficiency.
The Baseline Metrics
The most commonly cited metric for efficiency is Field Goal Percentage (FG%). This is the easiest and most intuitive way to measure efficiency, as the process simply requires dividing the number of field goals a player converts by the number of field goals attempted. One of the main problems with this number is that it fails to account for the value of the shots taken by the player. A 3-point shot is worth more to a team than a 2-pointer, yet both are treated as equally valuable shots when using FG%. A player who just shoots 3-pointers only has to shoot 33% from the field to match the points per shot of another player shooting 50% from the field but only on 2-point shots. In other words, players who take and make more three-pointers are more efficient. This 17% margin indicates that further context is required to determine a player's efficiency. While FG% is oftentimes paired with a 3-point percentage(3P%) to account for this lack of contextualization, the 2 values on their own are not reliable, and the number of 2-point and 3-point attempts taken by a player need to be accounted for. Looking at 5 or 6 numbers to determine a player's efficiency is, as ironic as it is, inefficient, and statisticians have created better algorithms for quantifying a player's efficiency.
Effective Field Goal Percentage and True Shooting Percentage
Effective Field Goal Percentage(EFG%) is a modified efficiency metric that weights 3-pointers accordingly in order to favor stronger shooters. The formula for EFG% is:
(FGM + 0.5 * 3PM) / FGA
Where FGM stands for Field Goals Made, 3PM stands for 3-Pointers Made, and FGA stands for Field Goals Attempted.
EFG% is a much better metric than FG% because it addresses the problems mentioned in the section above. Instead of taking 5 or 6 different data points, we can combine them all into 1 number that takes into account the significance of both 2 and 3-point shot attempts.
True Shooting Percentage(TS%) goes even deeper than EFG% does. True shooting percentage is a measure of shooting efficiency that takes into account not only field goals and 3-point shots, but also free throws. The formula for TS% is:
PTS / (2 * (FGA + 0.44 * FTA))
Where PTS is Points Scored, FGA is Field Goals attempted, and FTA is Free Throws attempted
TS% is important to consider because of how Free Throws can affect a player's scoring output. A player can score 10 points while shooting 1/10 from the field and 8/8 from the free-throw line. FG% or EFG% would indicate that this player was incredibly inefficient this game, while TS% would acknowledge the 4 possessions where he got fouled and shot perfectly at the charity stripe. Since there is virtually no difference between scoring on 4 possessions and hitting 8/8 Free Throws, (Some would argue that 8/8 Free Throws is even better because it places the opposing team in foul trouble) it is important to credit or criticize players for how well or poorly they shoot their free throws.
The difference between the 3 statistics can be seen by comparing a list of the most efficient performers according to each one.
NBA 2020-2021 Regular Season FG% Leaders as of April 12
Rudy Gobert-Center (66.4%)
Richaun Holmes- Center (64.4%)
Jarrett Allen-Center (63.3%)
Jakob Poetl-Center (62.8%)
Montrezl Harrell-Center (62.5%)
Zion Williamson-Power Forward (62.1%)
Deandre Ayton-Center (61.5%)
Enes Kanter-Center (60.7%)
Mason Plumlee-Center (60.3%)
Clint Capela-Center (59.9%)
Thaddeus Young-Power Forward (58.2%)
Jonas Valenciunias-Center (57.0%)
Nikola Jokic-Center (56.7%)
Bam Adebayo-Center (56.5%)
Giannis Antetokounmpo (56.5%)
NBA 2020-2021 Regular Season EFG% Leaders as of April 12
Joe Ingles-Small Forward (70.3%)
Rudy Gobert- Center (66.4%)
Joe Harris- Small Forward(66.3%)
Richaun Holmes-Center (64.6%)
Jarrett Allen-Center (64.1%)
Michael Porter Jr.- Small Forward (63.1%)
Jakob Poetl-Center (62.8%)
Zion Williamson-Small Forward (62.6%)
Montrezl Harrell-Center (62.5%)
Mikal Bridges- Small Forward (62.1%)
Deandre Ayton-Center (61.9%)
Duncan Robinson-Shooting Guard (61.7%)
Enes Kanter-Center (60.7%)
Doug Mcdermott-Small Forward (60.7%)
Nikola Jokic-Center (60.6%)
NBA 2020-2021 Regular Season TS% Leaders as of April 12
Joe Ingles-Small Forward (72.3%)
Ivica Zubac- Center (69.0%)
Richaun Holmes-Center (67.7%)
Jarrett Allen-Center (67.6%)
Rudy Gobert- Center (66.9%)
Joe Harris- Small Forward(66.3%)
Zion Williamson-Small Forward (65.9%)
Kevin Durant-Small Forward (65.7%)
Montrezl Harrell-Center (65.3%)
Robin Lopez-Center (65.0%)
Stephen Curry-Point Guard (64.9%)
Mikal Bridges- Small Forward (64.8%)
Michael Porter Jr.- Small Forward (64.8%)
Deandre Ayton-Center (64.3%)
Nikola Jokic-Center (64.1%)
While the FG% list is dominated by Power Forwards and Centers, the subsequent lists are dominated by 3-point specialists. Players Like Steph Curry, Kevin Durant, Joe Harris, Joe Ingles, Mikal Bridges, and MPJ are all far more efficient than their FG% indicates because of their elite marksmanship on Free Throws and deep shots.
Possession Efficiency Index
Despite the progress made with the development of EFG% and TS%, these metrics only consider a player's efficiency when they create a shot attempt. However, players can also create and take away shot attempts from their team through offensive rebounding and turnovers. For example, if a player attempts multiple layups in the paint on the same possession after securing the offensive rebound, their overall efficiency will drop regardless of the metric used. But this shouldn't be the case because the player is actively creating new possessions for his team which generate further scoring opportunities. By contrast, the same principle should hold for a player who generates a lot of turnovers. A player who goes 2/2 from 3 and has 2 turnovers in 4 consecutive possessions is viewed as an incredibly efficient player with 100% efficiency when in reality they are able to convert on about half of their opportunities. To go a step further and actually determine how efficient a player is at both creating and executing scoring opportunities, we can use the Possession Efficiency Index(PEI), a new statistic that I created which accounts for the offensive rebounds and turnovers a player gets while still weighting 3-point shots and free throw attempts accordingly. Just like how we analyzed the difference in the value of 2-point and 3-point shots, we need to address the value of Turnovers against Offensive rebounds. On average, NBA teams score about 1.27 points per possession off of turnovers and only 1.19 points per possession off of Offensive rebounds. While both lead to high-quality shots for opposite teams, it is clear that teams tend to convert more on fastbreaks than they do on put-back attempts and kick-outs after offensive rebounds. This indicates that a turnover is more detrimental to a team than an offensive rebound is beneficial. We can apply this information to our True Shooting Formula to create a new algorithm for determining a player's efficiency.
PEI=100* (PTS / (2 * (FGA + 0.44 * FTA +TPG -0.94*ORB)))
It is clear that metrics such as FG% undervalue the impact of the 3-point shot and are favorable towards centers and paint dominant players. EFG% and TS% are able to accurately value the 3-point shot but still overestimate the value of heliocentric ballhandlers who turn over the ball at high rates. The PEI truly measures a player's ability to capitalize on their opportunities, making it the most effective metric to measure a player's efficiency on the court.
Edited By: Gohitha Venkluri
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