Basketball, especially in the NBA, is a game that moves quickly – with this comes a lot of responsibility on the referees to make a fair call and to be at the top of their game.

However, it's common to hear discussions about how much influence referees have over the game and claims that their decisions ultimately decided an outcome. In this article, we took a data-driven approach to explore whether teams should change their tactics based on the referees in charge and what we can learn from analysing referee tendencies.

We analysed fouls called during the regular season across 2016-2020

To start the investigation, we used Tableau to plot referees by the number of games refereed in that season and the number of fouls called per game to test an initial hypothesis that refereeing more games leads to a higher propensity to blow the whistle. We applied a linear regression to fit the data and the outputs looked like this:

We found the results to be statistically significant, with a p-value less than 0.05 for all four seasons (small is good in case stats isn’t your specialty).

In equation form it looks like this:

2016-17: Fouls per game = 0.039 × games refereed + 11.890
2017-18: Fouls per game = 0.051 × games refereed + 10.777
2018-19: Fouls per game = 0.064 × games refereed + 10.441
2019-20: Fouls per game = 0.072 × games refereed + 10.503

As an example to decipher this, the 2016-17 equation means that a referee in their first game would be expected to issue 11.9 fouls, and for each game refereed they would issue an additional 0.039 fouls. Turning that around, it’s one additional foul for every 25 games refereed.

Over time that rate has sped up, with the additional foul coming in 19 games in 2017-18; 16 in 2018-19; and just 14 in 2019-20. That suggests an interesting area of exploration for NBA administration, who would be interested to strike the right balance between quality refereeing and free-flowing entertainment. There’s a future article there, for now we’ll stick with a game strategy view.

So can we strategise around this?

Not quite yet. Overall, while our initial hypothesis was supported by the analysis, the findings are risky to draw conclusions from without additional data such as referee roles and their positioning during the game, since these factors influence their authority and visibility to call fouls.

Nonetheless, the results demonstrate the potential value of adopting a data-driven approach to game strategy and how teams can leverage referee tendencies by analysing the data to formulate tactics.

Perhaps a more effective game strategy involves considering the specific referee rather than simply the number of games refereed. For instance, Scott Foster is regarded as the worst-rated referee and overly officious; an observation supported by the data, which shows that Foster issued fouls above the median in all four regular seasons. Coaches and players might do well to adjust their tactics and exercise more caution when he is officiating.

That said, Tony Brothers came out on top as the highest rated referee (in the same article). Brothers is seen to bring a different dynamic to the game, with players warming to his personal style. Interestingly though, Brothers has likewise issued fouls well above the median, and only 0.56 fewer fouls per game than Foster. He might do it with a smile and a friendly comment, but putting aside the nice vibes, the data shows players can expect to hear the whistle plenty of times under Brothers’ watch.

2022-23 regular season

With an average of18.8 fouls per game, 2022-23 NBA regular season has seen a continuing affect of referees issuing fouls at a high rate, leading to more stoppages in play and making it more challenging for teams to change their game plans. Saying that, Tony Brothers and Scott Foster remain in the top five referees for issuing the most fouls, with 227 and 218 fouls, respectively.

While we can't wait to see what the playoffs tell us, who is your favourite (or most despised) referee? Give them a shout-out, and we'll find where they sit on the scatter plot.

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