Are sports winners more violent than sports losers?
The [research] team focused on the 106 international rugby or soccer matches between 1995 and 2002. On non-match days, the number of assault victims averaged 21 per day, and on match days when Wales lost this rose to 25. But the situation was worse after a win, with 33 admissions per day on average…
Match days would seem to organize groups of rowdies, if nothing else; winning might embolden their violence. And don’t forget about alcohol. Read more here. Here is a related account.
Addendum: Thomas Edwards points to this explanation.