The demographics of the sport also play a role. Kick It Out estimates that in professional soccer, about 30 percent of the top-level players in England are black, with the figure slightly less for the rest of Europe. By contrast, there are only a handful of black coaches, referees and front-office staff members, and across Europe, very few black fans are season ticket holders. While Europe is increasingly black and Arab, most fans at stadiums are working-class whites.
"It is fair to say -- and Italy is probably the best place to illustrate this -- the demographics of football fans is still largely working class," Green said. "The lower working class, even though they make up a smaller percentage of the base, make up for well over half to two-thirds of the violent incidents."
Jason Perryman left court in Blackburn, England, last month after being fined $1,900 and banned for five years from soccer stadiums for racist behavior.
(Martin Rickett -- Pa Via AP)
One black player, Brian Tevreden, 23, who plays for the Dutch team Emmen, says he finds the unruly fan behavior insulting and will leave the field if he hears taunts in future games. "If they make monkey noises, I will go from the pitch," he said in a telephone interview. "The whole team will walk off the pitch."
Tevreden, who came to the Netherlands from Surinam when he was 6 years old, said that among spectators exhibiting such offensive behavior, "60 percent are racist. I think 30 percent are just trying to be funny."
A spokesman for the Royal Dutch Football Association said his organization was taking the matter seriously. Two months ago, the association passed regulations allowing a referee to stop a match because of excess noise or abuse from fans, said Frank Huizinga. Under the guidelines, the referee will talk to the heads of the competing clubs and consult with local officials before deciding whether a match can continue.
The association is also exploring ways to use technology, either to drown out abusive spectator noise with competing noise or to create a noise-free zone on the field.
British news media expressed outrage about the fan behavior during the Nov. 17 match against Spain, and many said it called into question Spain's bid to host the 2012 Olympics. But some Spanish media said British journalists were exaggerating the incident to cover up for the English team's loss of the game. "Perhaps it was because their team had played so poorly and they wanted to divert attention towards this muddled issue," said the Spanish daily newspaper ABC.
The next day, Spanish officials reacted to the disruptions, but seemed to cast doubt on what really occurred. "I condemn without doubt the racist displays that may have happened," said Education Minister Maria Jesus San Segundo. "These kinds of comments are deplorable and we do not want them to be made at all, either at sporting events or in society in general."
The abuse at the England-Spain match followed an incident involving Spanish team coach Luis Aragones, who used a racial epithet to describe Arsenal player Thierry Henry. Aragones later explained that he was merely trying to motivate one of his own players.
Sepp Blatter, the president of FIFA, said it was essential that soccer "eradicate the scourge" of racism.
"There is no room whatsoever for racism or discrimination in our sport," he said in a statement. "On the contrary, football is a tool for building bridges and nurturing tolerance. The world is already full of conflict that has its roots in racism and discrimination."
Special correspondents Alexandra Topping in Paris and Misja Pekel in Amsterdam contributed to this report.