Environmental change for one. example Syria losing half its agriculture land due to climate change has a lot to do with their poverty increase which then has other downstream consequences (ISILs numbers grow -> more terrorism -> increased military spending -> govts invasion of privacy). Add on that the shoe has yet to drop for most consequences related to climate change - yet it's still real and happening today.

Add to that culture and knowledge exchange effects and I'm pretty sure income distribution, while easily measured, would not be towards the the top.