Police Party Hearty

The following article: http://www.foxnews.com/story/0,2933,294076,00.html states that the town was not compromised by the police all being off duty. I would be curious to see what the crime rate was that night. If it was a small enough town, it probably didn't have much if any effect. And while we know that more police on the streets does result in a decrease in crime, has anyone done a study of what happens in the absence of police?