In 2007 a study by Joseph Price and Justin Wolfers drew widespread attention to implicit racial bias in NBA referee calls – namely, that white referees called fouls against black players more often than against white players (and vice-versa). The authors recently revisited the issue and found something surprising: since the publication of their paper that bias had completely disappeared.
The graphic below looks at foul-calling against white and black players based on the racial make-up of the three-man officiating referee crews. The first chart, of the time period immediately prior to the publication of the 2007 study, shows that the more white referees are involved in a game, the fewer fouls are called against white players, with a much smaller decline for black players. Study author Justin Wolfers calls this difference “small, subtle and significant.” The second chart looks at the period after the study came out and shows two things: the first is that there’s no longer a meaningful difference in foul calls based on referee make-up. Second, the overall number of foul calls decreased slightly.