This TED talk by Steven Pinker is pretty interesting. I’ll let all of his side comments, such as crediting Bill Clinton with the decline of violent crime in the 1990s, go. The most interesting aspect of this talk is not that violence is decreasing over time, but why violence is decreasing.
It seems pretty simple to me–violence has a very low return on investment.
Because of mass media, no act of violence seems isolated anymore. Therefore, committing an act of violence is a PR nightmare. Maybe not for individuals, but for states most definitely (Iraq). And states themselves have decreased the profitability of violence by individuals. It is virtually impossible for an individual to successfully take any significant amount of property from someone else by force (without penalty).
That’s why people rob banks without weapons. The rewards of successfully robbing the bank without a gun are equal to those of robbing a bank with a gun, but the risk of being unsuccessful is much less because the penalty for using a weapon in such a crime is greater.
It is sort of interesting to consider cultures that believe violence will be rewarded in the afterlife. There seems to be a definite perceived benefit to violence there.