Several times on this blog I have wondered why crime rates have fallen, and talked about how little we really do understand about historical causation, even about events that are readily visible, with a lot of data. The current riots in the UK would qualify as well. Those are on video, are extensively covered and investigated, and no one seems to have any real idea of what is causing those events.
But I have a possible explanation for the larger secular trend in falling crime rates: we are being protected by higher obesity. Or, at least, the two events are not separate, but are somehow related.
What? Of course I haven't actually run the numbers! Do you really want me to take grants from the mouths of deserving graduate students?
But think about these two large, visible, and inexplicable trends. Crime has steadily dropped over the past two decades. Obesity has just as steadily risen. Coincidence? I don't think so!
Does a packing a little extra weight make you just that much less likely to go out and commit a physically challenging violent crime? Or, maybe, does the same thing that make you fat make you less violent? This could be sitting around and playing violent video games while eating snack food. You're not out committing real crimes, and you're getting fat. Getting kids out for healthy outdoor exercise might be the worst thing we could do for our own safety.
Is the weight gain among the key crime-committing demographic, young males, correlated with decreased crime? Come on, grant-seeking grad students. Step up to the plate.
Meanwhile, I will continue to indulge in unrestrained speculation, unhandicapped by having to run nasty regressions on piles of recalcitrant data.