New Scientist has a story about some research by Vaseekaran Sivarajasingam at Cardiff University into violence on game days at the local pitch.
Sivarajasingam looked at emergency room admissions for assault from 1995 to 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.
Suggested avenues for further study: drunken revelry. From the paper: “Winning prompts celebration, a key component of which is alcohol consumption, and prompts the formation of crowds of intoxicated individuals, making interpersonal physical assertiveness more likely.”