The Three Point Puzzle
By Jack Lamb | November 10, 2020
If you have ever watched basketball you have probably had the question of why teams do not only shoot three pointers because they are worth more points. You soon realize that teams convert on a much lower percentage of three pointers than two pointers so it stands to reason that shooting three pointers all the time would not be beneficial to the team. But the next question that many basketball fans wonder is what percentage of three pointers a team would have to make in order for a team to only want to shoot three pointers. This is the question that I attempt to answer. The NBA three point average across all thirty teams in the 2018-2019 season (the last season before Covid-19) was 35.5 percent with an average number of attempts per game at 32. This leads to an average of 34.08 points per game coming from the three ball. Using the same logic as outlined above, NBA teams scored an average of 59.4 points per game from two pointers and 17.7 points per game from free throws. Adding these three values up gives us an expected value of 111.2 points per game for the average NBA team. The diagram below shows the average points per game of every NBA team during the 2018-2019 season. The last data point at the far right of the bar chart shows the average points per game of all of the teams (same as we found above).
By dividing the league average points per game of 111.2 by 3 points per attempt, a team would have to make 37 three pointers in order to score enough points to equal the league average. 37 three pointers is already five more than the average number of three point attempts in the 2018-2019 NBA season (32 Attempts). To find the percentage that a team would have to shoot from three point range in order for this to be feasible with the average 89.2 field goal attempts per game, I divided 37 by 89.2. The result was that if conditions stayed the same for each attempt as in the 2018-2019 season, then a team would have to shoot 42 percent from three point land in order to equal the expected value of 111.2. As you can see in the bar graph below, only five teams shot above 37 percent from behind the three point line. Those teams were the Golden State Warriors, The Los Angeles Clippers, the Sacramento Kings, the San Antonio Spurs, and the Indiana Pacers. In the 2018-2019 season, the San Antonio Spurs had the highest three point percentage of any NBA team at 39.2 percent which is just 2.8 percent away from the 42 percent needed to equal the expected value of 111.2.
In all actuality, the gap between these teams and the 42 percent mark is much higher than it seems on paper. For one, if a defense sees that a team is only shooting three pointers, they will guard in a way that makes it much more difficult for a team to shoot threes, thus making their three point percentage go down. More insight into how defenses would change with an increase in three point attempts would be needed in order to truly answer this question. If defensive conditions stayed the same as three point attempts increased the magic number in terms of three point percentage needed would be 42 percent, but as discussed earlier, this is purely hypothetical.