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Though they’ve risen to the top of their profession and work in front of huge audiences, NBA referees aren’t immune to unintentional racial bias when it comes to calling fouls, according to a new study.

Economists Joe Price of Brigham Young University and Justin Wolfers of the University of Pennsylvania found that players get called for 4 percent fewer fouls by officials of their same race.

It’s not something the refs think about or intend to do, the researchers say. Instead, it appears to be a result of “implicit bias” – subtle mental associations that surface when people are forced to make snap judgments.

Though a majority of players are black and a majority of refs are white, the integrity of NBA officiating isn’t the point of the research. Professional basketball just happens to be a data-rich industry that provides insight into human behavior and the game of life.

“In most situations it’s hard to disentangle explicit bias from implicit bias,” Price said. “What made our study unique is documenting the effect in a high-stakes, real-world situation.”

If the topic sounds vaguely familiar, it’s because the project made a stir in its early stages when Price was wrapping up his Ph.D. at Cornell. At the time, the league refuted the suggestion of biased officiating. Since then Price and Wolfers’ study has survived the scrutiny of reviewers at the Quarterly Journal of Economics, a top-tier scholarly journal that will publish the article Dec. 3.

The analysis included stats on every player and game during a span of 13 seasons. The data set also includes the racial makeup of the three-person officiating crew assigned to each game. Details on the research methods are fully described here.

For students of the game, the study offers several other intriguing findings:

  • No single referee in the analysis stood out as being more or less biased in their calls, which strengthens the case that it happens unintentionally.
  • For flagrant and technical fouls – considered more subjective decisions – the racial bias manifests at about the same 4 percent rate seen with all fouls.
  • A coach’s race also seems to subtly influence the decisions of referees, and it’s about equal to the effect of one player’s race.

Basketball is no longer the only arena where this kind of research is playing out. Prompted by Price and Wolfers’ NBA study, Professor Dan Hamermesh of the University of Texas at Austin looked to baseball. His examination of balls and strikes called by home-plate umpires in Major League Baseball found a racial bias affecting one of every 200 pitches on average.

More importantly, Hamermesh and his co-authors suggest in a forthcoming article that it is possible to overcome implicit racial biases. When the stakes got higher, the bias disappeared. For example, umpires exhibited no bias with pitches that could end the at-bat with a called “strike three” or “ball four.”

“The results suggest that raising the ‘price’ of discrimination, in this context and perhaps generally, leads it to be overcome,” said Hamermesh.

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