May 2, 2007
Study of N.B.A. Sees Racial Bias in Calling Fouls
By ALAN SCHWARZ
An academic study of the National Basketball Association, whose playoffs continue tonight, suggests that a racial bias found in other parts of American society has existed on the basketball court as well.
A coming paper by a University of Pennsylvania professor and a Cornell University graduate student says that, during the 13 seasons from 1991 through 2004, white referees called fouls at a greater rate against black players than against white players.
Justin Wolfers, an assistant professor of business and public policy at the Wharton School, and Joseph Price, a Cornell graduate student in economics, found a corresponding bias in which black officials called fouls more frequently against white players, though that tendency was not as strong. They went on to claim that the different rates at which fouls are called âis large enough that the probability of a team winning is noticeably affected by the racial composition of the refereeing crew assigned to the game.â
N.B.A. Commissioner David Stern said in a telephone interview that the league saw a draft copy of the paper last year, and was moved to do its own study this March using its own database of foul calls, which specifies which official called which foul.
âWe think our cut at the data is more powerful, more robust, and demonstrates that there is no bias,â Mr. Stern said.
Three independent experts asked by The Times to examine the Wolfers-Price paper and materials released by the N.B.A. said they considered the Wolfers-Price argument far more sound. The N.B.A. denied a request for its underlying data, even with names of officials and players removed, because it feared that the leagueâs confidentiality agreement with referees could be violated if the identities were determined through box scores.
The paper by Mr. Wolfers and Mr. Price has yet to undergo formal peer review before publication in an economic journal, but several prominent academic economists said it would contribute to the growing literature regarding subconscious racism in the workplace and elsewhere, such as in searches by the police.
The three experts who examined the Wolfers-Price paper and the N.B.A.âs materials were Ian Ayres of Yale Law School, the author of âPervasive Prejudice?â and an expert in testing for how subtle racial bias, also known as implicit association, appears in interactions ranging from the setting of bail amounts to the tipping of taxi drivers; David Berri of California State University-Bakersfield, the author of âThe Wages of Wins,â which analyzes sports issues using statistics; and Larry Katz of Harvard University, the senior editor of the Quarterly Journal of Economics.
âI would be more surprised if it didnât exist,â Mr. Ayres said of an implicit association bias in the N.B.A. âThereâs a growing consensus that a large proportion of racialized decisions is not driven by any conscious race discrimination, but that it is often just driven by unconscious, or subconscious, attitudes. When you force people to make snap decisions, they often canât keep themselves from subconsciously treating blacks different than whites, men different from women.â
Mr. Berri added: âItâs not about basketball â itâs about what happens in the world. This is just the nature of decision-making, and when you have an evaluation team thatâs so different from those being evaluated. Given that your league is mostly African-American, maybe you should have more African-American referees â for the same reason that you donât want mostly white police forces in primarily black neighborhoods.â
To investigate whether such bias has existed in sports, Mr. Wolfers and Mr. Price examined data from publicly available box scores. They accounted for factors like the playersâ positions, playing time and All-Star status; each groupâs time on the court (black players played 83 percent of minutes, while 68 percent of officials were white); calls at home games and on the road; and other relevant data.
But they said they continued to find the same phenomenon: that players who were similar in all ways except skin color drew foul calls at a rate difference of up to 4 ½ percent depending on the racial composition of an N.B.A. gameâs three-person referee crew.
Mark Cuban, the owner of the Dallas Mavericks and a vocal critic of his leagueâs officiating, said in a telephone interview after reading the paper: âWeâre all human. We all have our own prejudice. Thatâs the point of doing statistical analysis. It bears it out in this application, as in a thousand others.â
Asked if he had ever suspected any racial bias among officials before reading the study, Mr. Cuban said, âNo comment.â
Two veteran players who are African-American, Mike James of the Minnesota Timberwolves and Alan Henderson of the Philadelphia 76ers, each said that they did not think black or white officials had treated them differently.
âIf thatâs going on, then itâs something that needs to be dealt with,â James said. âBut Iâve never seen it.â
Two African-American coaches, Doc Rivers of the Boston Celtics and Maurice Cheeks of the Philadelphia 76ers, declined to comment on the paperâs claims. Rod Thorn, the president of the New Jersey Nets and formerly the N.B.A.âs executive vice president for basketball operations, said: âI donât believe it. I think officials get the vast majority of calls right. They donât get them all right. The vast majority of our players are black.â
Study of N.B.A. Sees Racial Bias in Calling Fouls
By ALAN SCHWARZ
An academic study of the National Basketball Association, whose playoffs continue tonight, suggests that a racial bias found in other parts of American society has existed on the basketball court as well.
A coming paper by a University of Pennsylvania professor and a Cornell University graduate student says that, during the 13 seasons from 1991 through 2004, white referees called fouls at a greater rate against black players than against white players.
Justin Wolfers, an assistant professor of business and public policy at the Wharton School, and Joseph Price, a Cornell graduate student in economics, found a corresponding bias in which black officials called fouls more frequently against white players, though that tendency was not as strong. They went on to claim that the different rates at which fouls are called âis large enough that the probability of a team winning is noticeably affected by the racial composition of the refereeing crew assigned to the game.â
N.B.A. Commissioner David Stern said in a telephone interview that the league saw a draft copy of the paper last year, and was moved to do its own study this March using its own database of foul calls, which specifies which official called which foul.
âWe think our cut at the data is more powerful, more robust, and demonstrates that there is no bias,â Mr. Stern said.
Three independent experts asked by The Times to examine the Wolfers-Price paper and materials released by the N.B.A. said they considered the Wolfers-Price argument far more sound. The N.B.A. denied a request for its underlying data, even with names of officials and players removed, because it feared that the leagueâs confidentiality agreement with referees could be violated if the identities were determined through box scores.
The paper by Mr. Wolfers and Mr. Price has yet to undergo formal peer review before publication in an economic journal, but several prominent academic economists said it would contribute to the growing literature regarding subconscious racism in the workplace and elsewhere, such as in searches by the police.
The three experts who examined the Wolfers-Price paper and the N.B.A.âs materials were Ian Ayres of Yale Law School, the author of âPervasive Prejudice?â and an expert in testing for how subtle racial bias, also known as implicit association, appears in interactions ranging from the setting of bail amounts to the tipping of taxi drivers; David Berri of California State University-Bakersfield, the author of âThe Wages of Wins,â which analyzes sports issues using statistics; and Larry Katz of Harvard University, the senior editor of the Quarterly Journal of Economics.
âI would be more surprised if it didnât exist,â Mr. Ayres said of an implicit association bias in the N.B.A. âThereâs a growing consensus that a large proportion of racialized decisions is not driven by any conscious race discrimination, but that it is often just driven by unconscious, or subconscious, attitudes. When you force people to make snap decisions, they often canât keep themselves from subconsciously treating blacks different than whites, men different from women.â
Mr. Berri added: âItâs not about basketball â itâs about what happens in the world. This is just the nature of decision-making, and when you have an evaluation team thatâs so different from those being evaluated. Given that your league is mostly African-American, maybe you should have more African-American referees â for the same reason that you donât want mostly white police forces in primarily black neighborhoods.â
To investigate whether such bias has existed in sports, Mr. Wolfers and Mr. Price examined data from publicly available box scores. They accounted for factors like the playersâ positions, playing time and All-Star status; each groupâs time on the court (black players played 83 percent of minutes, while 68 percent of officials were white); calls at home games and on the road; and other relevant data.
But they said they continued to find the same phenomenon: that players who were similar in all ways except skin color drew foul calls at a rate difference of up to 4 ½ percent depending on the racial composition of an N.B.A. gameâs three-person referee crew.
Mark Cuban, the owner of the Dallas Mavericks and a vocal critic of his leagueâs officiating, said in a telephone interview after reading the paper: âWeâre all human. We all have our own prejudice. Thatâs the point of doing statistical analysis. It bears it out in this application, as in a thousand others.â
Asked if he had ever suspected any racial bias among officials before reading the study, Mr. Cuban said, âNo comment.â
Two veteran players who are African-American, Mike James of the Minnesota Timberwolves and Alan Henderson of the Philadelphia 76ers, each said that they did not think black or white officials had treated them differently.
âIf thatâs going on, then itâs something that needs to be dealt with,â James said. âBut Iâve never seen it.â
Two African-American coaches, Doc Rivers of the Boston Celtics and Maurice Cheeks of the Philadelphia 76ers, declined to comment on the paperâs claims. Rod Thorn, the president of the New Jersey Nets and formerly the N.B.A.âs executive vice president for basketball operations, said: âI donât believe it. I think officials get the vast majority of calls right. They donât get them all right. The vast majority of our players are black.â
