Interesting article. Learned a new buzzword: "acquaintance violence". In the UK I assume that means "to be attacked by someone to whom you have been properly introduced".

So, use of knives in "crimes of passion" are decreasing because fewer people have a knife handy when they happen to snap. Doesn't say if the same number of people were just clobbered with rocks instead.

On the other hand, robberies and other attacks on strangers with knives are increasing - perhaps because the robbers know that the victim is now less likely to be armed?