Luck/Turmoil versus Nothing.

[Finalgenesis]

I think that's a linked event, one province gets poploss "immigrate out" then there's also one in the same turn getting "immigrate in". If you score the immigrate in event, your pop gain is 20% of whatever the immigrate out province is. I've seen both end of the events, so I'm assuming this is how it works.

If you get lucky and there's an immigrate out event in enemy capital to one of your province, you can potential see up to 6K+ pop boost

I think the immigration is anywhere, not adjacent, as I got immigrate event in one of my provinces thats at the heart of my territories. Now if I can figure out some way to interrupt their migration and steal the pearls they use to teleport... Thats a lot of pearls