Attila tips and un-/under-documented features

[Philippus Flavius Homovallumus]

So what's the deal with the WRE's Constant Immigration trait?

I'm about 100 turns in and immigration is causing -9 PO everywhere. If that gets any higher then not amount of PO buildings will save me - the well managed and prosperous WRE will implode because of "reasons".

So my question is - what does "Constant Immigration" mean?

Edit: Half the ERE is a smoking ruin, I wondered what the Huns were doing - they've got as far as Egypt now and they raised the entire Levant, if that's what's causing all this immigration then I think I'll keep plugging away, otherwise might need to leave it because if immigration gets any worse I won't be able to sustain the Empire.