Ahh, of course thats it! the breakdown of the family unit. Because in the days of Queen Victoria when there really could have been no stronger bond in the family, there was hardly any crime! Oh wait....
Just because theres a pattern does mean thats it. When people sent their kids to work in factories from 6yrs onwards i'm sure there was less child crime too, doesn't mean we should pack the kids off to mills.
I would also point out that crime has been rapidly on the rise since the breakdown of the community. Because we all live in our little boxes not giving a shit about one another, we couldn't care less if we stole off each other. In the mining villages of midlands and northern England there were very tight communities, and very low crime rates. Part of the reason is that everyone knows everyone, so you get to like your neighbours, and word gets around fast if your thought a thief, and you do not want a village full of miners after you. The mines closed down, the community fell apart and crime rose drastically.