assimilation depends on government's ideology. communist government base their policy on lower classes (proletariat=Farmers+Labourers) and full citizenship. assimilation of lower classes must be quick with rule of communists and very low with fascism. democracy has some special features too.
We have worked out a new system for Victoria 2. We have a new Borg Pop that handles all assimilation issues for us. its a very elegant system.