Do poorer countries participate more in physical violence toward each other?

I have noticed a pattern. I have noticed through reading the news and history books that pooer countires have the most civil wars and the most macres. Rwanda, Sri Lanka, parts of Indonesia, Sudan, etc. Also in Suth and Sntral America. I have also noticed this patter right here in America in lower income neighborhoods, with gangs and shooting. The shooting can really get out of hand in a lot of areas with innocent bystanders getting struck,including chidren. I have read somewhere that the more underdeveloped a person or group is mentally, that the more aggressive they act. This may or may not be innate. It could be the way they were raised, there is the whole nature versus nurture debate pertaining to generational poverty. What do you think?