An Australian group/think tank has produced its 11th annual report which makes interesting reading:
http://visionofhumanity.org/app/uploads/2017/06/GPI-2017-Report-1.pdf
The UK comes in at No.41 and the USA No.114 in the list of most peaceful countries (assessed before the Manchester incident) in the world - Iceland, New Zealand and Portugal are the top three, Iceland holding top position for the eighth consecutive year.
It is the explanation of the basis for the rankings and the wealth of information that comes out in this that to me is interesting. One thing that struck me was the figure for the total cost of violence (of all types, including the military element) - to me it is very high. On the whole though there has been a small worldwide improvement, in spite of everything.