From The New York Times:
The study, conducted over a 13-season span through 2004, found that the racial makeup of a three-man officiating crew affected calls by up to 4 1/2 percent.
The NBA strongly criticized the study, which was based on information from publicly available box scores, which show only the referees' names and contain no information about which official made a call.
"The study that is cited in the New York Times article is wrong," president of league and basketball operations Joel Litvin told The Associated Press on Tuesday night. "The fact is there is no evidence of racial bias in foul calls made by NBA officials and that is based on a study conducted by our experts who looked at data that was far more robust and current than the data relied upon by Professor Wolfers.
"The short of it is Wolfers and Price only looked at calls made by three-man crews. Our experts were able to analyze calls made by individual referees."
Litvin said the NBA's study, using data from November 2004 to January 2007, included some 148,000 calls and included which official made each call. The Times said the NBA denied a request by Wolfers and Price to obtain that information, citing its confidentiality agreement with the officials.
I am going to go out on a limb here and say that white refs usually call more fouls on black players because.......THERE ARE MORE BLACK PLAYERS!!!!
This is ridiculous.