The FBI has reported that crime in America has dropped significantly - from The Daily
There is no definitive take on why crime is declining. Robbery declined by 9.5 percent, undermining the intuitive view that high unemployment contributes to property crime. The United States is more unequal in 2011 than it was in 1991, so the notion that crime flows from relative economic deprivation doesn’t seem to fit.
The article then goes on and reasons that an aging population will have reduced crime.
Another reason I haven't seen touched on is modern technology. We are more connected than ever with cellphones, email and Facebook. It's now easier than ever to report crimes, and even take video or photos of the perpetrators. The time for the criminal to "get away" has been reduced, making crime even riskier than before. Gone are the days when you could rob someone and then easily make your getaway before anyone could react. The outlaws of yesteryear would be shocked.
Social networking can also warn friends and family of potential and known troublemakers. For example, the so-called "bad penny" can be easier to identify by their interactions on Facebook.
Of course the (inflation adjusted) cost of consumer goods has decreased too - televisions, game consoles and computers just aren't worth what they used to be, making Breaking and Entering less profitable.