The drop in violence is enormous and visible in crime rates across basically any age demographic you look at. It’s not just a function of an aging society. It also doesn’t seem obviously correlated with policing, since it exists across cities with radically different policing regimes. A lot of people think it has to do with environmental factors, and specifically lead.
> A lot of people think it has to do with environmental factors, and specifically lead.
Ironically, we are studying whether lead caused cohesion problems for the Roman Empire [1] [2], so it isn't as if we didn't suspect lead before to cause civilization-scale problems. And while the modern drop in blood lead levels is big in the developed world [3], it is still orders of magnitude greater than pre-industrial levels.
