Not sure about last 10/20 years but I can recommend "The Better Angels of Our Nature: Why Violence Has Declined" by Steven Pinker for a deep analysis of the development of Violence. He also states the development of wars and their heaviness.
Discussion
Its mainly Data until 2000. What do you want to analyze? Maybe I can find some data in the book for your purpose.
I was in a discussion with someone, and the person was arguing, that the situation today is better then in the past. I only have a subjective feeling about it, hence I was interested in some more data and arguments.
Thanks for Steve Pinker recommendation 🙏🏽
Here is some data which might He useful 
