Western Herzegovina is not part of Croatia, what's the point of including in in discussion? And today it's richest part of BiH.
Krajina was underdeveloped for centuries and not because of communists lol. It served as military zone for long and there was nothing there except army barracks and most simple infrastructure.
It's poorest part of Croatia for very long time.
Literacy in Kingdom of Yugoslavia in 1930
https://i.redd.it/zdt5xc7glq001.jpg
Serb-majority Krajina being far below literacy of Croatia-Slavonia and coastal Dalmatia, on same level like Ottoman ruled Balkans.