The modern interpretation of "bread and circuses": Subsidized food and broadband ubiquity with 24/7 access to whatever stimulates and titillates (sex, violence, a captive audience) can lead to a more sedate populace. Of course, that was one factor that led to the decline of the Roman Empire, too. When you've got a pretty sweet deal going, why risk going to jail and messing it all up?
I'd also like to see if the rise in the access, use and broad social acceptance of pharmaceutical opiates, anti-psychotics, and anti-depressants is also contributing to the decline. You can't really go out and rape and murder if you're hopped up on goofballs.