The source: “The Influence of Social Forces: Evidence from the Behavior of Football Referees” by Thomas J. Dohmen, in Economic Inquiry, July ­2008.

Fans have long suspected it, but now comes ammunition for that next barroom argument: Referees really do favor the home team. Thomas J. Dohmen examined a ­decades’ ­worth of statistics from the Bundesliga, Germany’s 18-team premier soccer ­league—­more than 3,500 ­matches—­and found that there was a measurable bias toward the home team when it came to decisions on stoppage time (time added at the end of regulation play for minutes lost through substitutions, players’ injuries, etc.), penalty kicks, and goals. The phenomenon be­came more pronounced when home-team fans outnumbered those rooting for the visitors, when the home team was only a goal behind, and, revealingly, in stadiums without a running track between the stands and the ­field.

Were there raised eyebrows at Maastricht University in the Netherlands when Dohmen, a professor there, proposed looking at soccer games for deep insights into human behavior? Perhaps, but the Bundesliga offered him a unique opportunity to assess the referees’ decisions since each game is also scrutinized by an “official observer of the DFB,” the governing body of the ­league.

Even though referees risk losing pay if they make biased rulings, Dohmen found subtle, though mea­sur­able, evidence that they favor the home team. He was unable to pinpoint the exact cause. The most likely explana­tion is “that social pressure from the crowd directly affects the referee,” a conclusion buoyed by the higher incidence of favoritism in ­track-­less stadiums (where the partisan crowd is closer to the action). It could be that referees respond subcon­sciously to the fervor generated by a close game; the crowd wants the suspenseful match to continue and the referee accedes to this desire by rewarding additional game min­utes.
Or, in the most indirect hypothesis, ­home-­team players may be spurred by rabid fans to complain more vociferously about the officiating, badgering the referee into making calls in their favor. Dohmen finds this idea the least plausible, but it, too, fits “the social pressure hypothesis.”

Dohmen cites a corroborating study in which professional soccer referees were shown videotapes of tackles in the English Premier League. One group watched with the sound off and called 15.5 percent fewer fouls against the home team than those listening to the crowd noise. Clearly, Dohmen says, “referees’ objective judgment capabilities are impaired by the emotional atmosphere in the stadium.” Coming soon to a stadium near you: overhanging stands with crowd noise amped really ­loud.