The joyrider on this statistical rocket is increasingly likely to be juvenile. Worldwide and throughout history, people who commit violence are nearly all young, from a low income family and male. Studies of identical twins and adopted boys prove that genes or biological makeup are very rarely involved. All the studies there have ever been have had similar findings. What is more, my theory accords with the broader picture.
Assaults are twice as common in poorer, developing nations as opposed to richer, developed ones.
Between developed nations, murder rates correlate strongly with the size of the gap between rich and poor in the nation - the more inequitable, the more murderous. North America has a very large proportion of its population living in almost shanty town conditions, with virtually no health or other welfare support. It also has by far the most millionaires. A 70s study found that the higher the levels of benefit, the lower the levels of violence in the States across America. But in the shorter term, it is not so easy to see what they can do.