Serbia is ranked on #85 on PPP (income per capita) while Slovenia and Croatia are a healthy 30+ positions ahead on this ranking (World Bank). I know Bosnia are poorer, but I didn't expect the difference between Serbia and Slovenia to be such a landslide. Didn't expect the average Serbiam to be poorer than Brazilian.
I am not looking to limit conversation here but you might consider posting this on /r/askeconomics as well as the reasons for this difference might fall within the last twenty years.
Follow up: was there such a difference at the time of Yugoslavia's break up?