The demotion bug causes very fast assimilation, ignoring cores - even backwards.
In the current version of the game, the calving of new POPs is highly restricted. To the best of my knowledge, the only phenomena that can create new POPs are:
- Promotion / Demotion: into an empty strata
- Migration: a new tiny POP will show up at the destination
- Religious conversion of pagan POPs
My understanding is that in Victoria II 1.0 POP calving was unrestricted, but this led to various problems and was removed in a later patch. Hopefully one of the old-timers can fill us in on the details.
Lets try a concrete (simplified) example:
Lets say the province of Moscow has only one POP, a size 300,000 Russian Orthodox Laborer - literacy 20% . Unemployment is very high and we have just built some factories there.
The next demotion tick that POP is going to decide that it wants to demote 1,000 and that they should demote to craftsmen.
The game looks at Moscow province and sees that there are no craftsmen pops so it creates one. Moscow now has two POPs:
- a size 299,000 Russian Orthodox Laborer - literacy 20%
- a size 1,000 Russian Orthodox Craftsmen- literacy 20%
This process continues and ten years later Moscow looks like this:
- a size 200,000 Russian Orthodox Laborer - literacy 20%
- a size 100,000 Russian Orthodox Craftsmen- literacy 20%
Lets run that again with one small change:
Lets say that in addition to the laborers Moscow has another POP size 10 Swedish Protestant Craftsmen - literacy 90%, who just migrated in from Alland.
The next demotion tick the laborer POP is going to decide that it wants to demote 1,000 and that they should demote to craftsmen.
The game looks at Moscow province and sees that there is a craftsmen pop so it doesn't need to creates one.
Moscow after the demotion tick:
- a size 299,000 Russian Orthodox Laborer - literacy 20%
- a size 1,010 Swedish Protestant Craftsmen- literacy 90%
This process continues and ten years later Moscow looks like this:
- a size 200,000 Russian Orthodox Laborer - literacy 20%
- a size 100,010 Swedish Protestant Craftsmen- literacy 90%
Moscow is now 33% Swedish and has an average literacy of 43% - all due to the power of demotion!
For all practical purposes this will continue until a Russian craftsmen POP wanders in from Kazan giving demotion a less goofy target
Now you may say, "Won't assimilation save us from this nonsense?" Well, sort of...
The next assimilation tick that large Swedish craftsmen POP is going to decide that it wants to assimilate by 100.
The game looks at Moscow province for an assimilation target pop, and it finds one - assimilation will be allowed to happen.
Valid targets for assimilation are National / Accepted culture POPs of the same Wealth level. Craftsmen are poor; laborers are poor - I think you see where this is going....
After the assimilation tick, Moscow looks like this:
- a size 200,100 Russian Orthodox Laborer - literacy 20%
- a size 99,910 Swedish Protestant Craftsmen- literacy 90%
Assimilation's only effect is to apply slight back pressure against the bug.
In the new world, where assimilation is strong, it is decently common to have a low demand farm RGO with sky high unemployment where the farmers are desperately trying to demote to craftsmen, but every month that is balanced perfectly by those craftsmen assimilating back down to farmers.
I have been meaning to write up a tutorial of doing this as Austria. I am sure everyone would love to see KUK with every province 50%+ German by the end of the game.