You also need to take into account people’s changing behaviours.
Let’s say there’s a neighbourhood where people get mugged a lot by the ruling gangs. If people stop going there, the muggings will drop and statistics will say the neighbourhood is safer. Of course, in reality the same gangs are still there and it is just as dangerous a place to visit. Statistics alone often don’t tell the real tale of societal collapse.
“If people stop going there, the muggings will drop and statistics will say the neighbourhood is safer. “
Yes, stuff like that happens on micro-scale. But this article talks about the country as a whole. So go here and have a look:
http://en.wikipedia.org/wiki/Crime_in_the_United_States