The Pudding Do NBA refs favor the home team? Analyzing 13,658 reviewed calls by the NBA to rank teams by favorable home court officiating By Oliver Roeder

The advantage of playing at home—whether it’s home court or field or rink or dojo—is universal in sports. Major-league baseball teams consistently win 54% of their home games, while their hockey counterparts take over 60%. The edge has been found in every year of English soccer, since 1888. With only a few exceptions, home-court advantage has appeared in every season of every major American sport since 1900. But nowhere has home advantage seen such a dramatic expression as in the NBA.

Home Field Advantage in Major American Sports Home team winning percentage in the NBA, NHL, NFL, and MLB, 1900 - present

In many of the NBA’s early seasons, home teams were regularly winning 66% of their games. But why? Perhaps home fans cheer on their local heroes to incredible feats. Perhaps the bed in a superstar’s mansion is more comfortable than the road hotel’s. Maybe stadiums have been fine-tuned to the liking of the home team. Maybe jet-lag hinders performance. Or maybe, under pressure from roaring and judgmental local crowds, it’s the officials. Since March 2015, the NBA began assessing referee calls (and notable non-calls) in the final two minutes of all games within five points, posting daily reports on its website. Last month, The Pudding compiled the data and open-sourced the results for public analysis. Does the home team receive favorable officiating? Does it explain the NBA’s home-court advantage? We can break down NBA calls into three categories: correct calls, incorrect no-calls, and incorrect calls:

In every category, the home team benefited. More infractions were correctly called on the away team. The away team is the victim of more incorrect calls. And the home team is the beneficiary of more incorrect non-calls. And while the edge seems real, its magnitude may be small: there are over 13,000 calls reviewed in this data set. Do certain teams benefit when they play at home? Let’s focus on just the referees’ mistakes (incorrect calls and incorrect non-calls) broken down by the league’s 30 teams in their home arenas.