A new National Bureau of Economic Research Working Paper, "Does Movie Violence Increase Violent Crime?", by Gordon Dahl and Stefano DellaVigna, reaches the interesting conclusion (based on mid-1990s U.S. data) that, at least in the short run, the dominant empirical effect of violent movies goes the other way. That is, more people watching violent movies in the theaters correlates with (and appears to cause) reduced violence.
Their data breaks down violent incidents by hours, with 6 pm to 12 am being the presumed viewing times and 12 am to 6 am the aftermath. For the first of these two periods, violence apparently declines due to incapacitation, i.e., the potentially violent are sitting in theaters watching violent movies instead of wandering the streets. From 12 am to 6 am the effect is even stronger, apparently reflecting substitution. Attendees have chosen going to the movie in lieu of drinking more and getting into violent situations.
Bottom line, "our estimates suggest that in the short run violent movies deter almost 1,000 assaults on an average weekend. While our design does not allow us to estimate long-run effects, we find no evidence of medium-run effects up to three weeks after initial exposure."
I have no dog in this fight, merely finding the result interesting and initially counter-intuitive. Next step, of course, is for someone to propose a Pigovian subsidy for movie violence so we will have the optimal level rather than too few given the positive externality. (Meant as a joke.)
Or, to reverse the big pay-off line in The Rocky Horror Picture Show, "don't be it, dream it."