A model of cultural assimilation

[Shadowstrike]

I always thought that the mechanisms to integrate new pops into your empire are too simplistic. Everyone is unhappy about being conquered for 10 years, and then completely forgets their prior lives once that time period is over. This not only feels wrong, it also makes creating multi-species empires way too easy. To address that, I've put together a model representing acculturation: i.e. how much pops feel like they belong to your nation.

Every sentient pop would gain an attribute called "national identity" (i.e. this excludes drones, robots/droids, and nerve-stapled pops). This would work a little like a pop's ethic: it has a single value (representing which nation that pop feels it belongs to), and has a chance to flip every month. After living in your empire for a sufficiently long period of time, the national identity of xeno pops will convert to the national identity of your nation, unless 1) you are fanatically xenophobe, 2) they are enslaved, or 3) you have a fanatic ethic, and that pop has the exact opposite ethic. On the other hand, if your nation has xenophile ethics and grants citizenship rights to the pops in question, they will culturally assimilate faster. Here's my proposal for the MTTH for each combination of your nation's ethics and the pop's citizenship status. (Assume 1 lifetime = 200 years for immortal pops.)

Fanatical Xenophile + citizenship: 1/2 a lifetime
Xenophile + citizenship: 1 lifetime
Citizenship: 2 lifetimes
Xenophile + residency: 2 lifetimes
Residency: 3 lifetimes
Xenophobe + Residency: 4 lifetimes
Fanatic Xenophobe, or Slavery, or Fanatical opposing ethic: Never

This MTTH would be modified by a few other attributes. A happier pop will assimilate faster, a higher strata pop will assimilate faster, and pops that share your ethos will assimilate faster (and ones that have the opposite ethos will assimilate slower). There should also be a bonus to assimilation time based on the proportion of pops on the planet with your national identity (representing having examples to acculturate to). Conquered pops, and liberated/refugee pops would retain their happiness bonuses/penalties (although those should extend to 1 lifetime, and the conquest penalty should be larger), which should make pops you conquer take longer to assimilate, while pops you save should assimilate faster. Further, there should be a modifier based on the "acceptance" of a pop (i.e. how much that species is seen as being "native" to your nation). That should be a nation-wide value for each species (seen on the species screen) representing how much a species is seen as "belonging" to your nation by pops at large. This would begin at 0, and start to tick up as pops of that species become accultured citizens.

It should also be possible for pops to lose your national identity, particularly if the circumstances are all against them (i.e. wrong ethos, low happiness, low strata, lots of non-national identity pops, xenophobe ethics, etc.) These pops can flip to the national identity of another nation where their species has a high acceptance value, or a "rebel" nation of your species with diametrically opposed ethics.

The proportion of pops with a "foreign" national identity should also feed into separatism. Planets with low happiness and a high proportion of pops that don't have your national identity will want to leave your nation and join the one matching their national identity. The exact proportion needed to break away should depend on your government form (50% for democracies, higher for oligarchies and even higher for imperial/dictatorial); you would get an option to allow this to happen, or try to suppress the separatist movement - which then feeds into an event chain leading to an uprising on that planet. You can of course suppress this with martial law, etc.

 

[nat.hol]

This is a very interesting model, and I would say that it all makes sense. However, it may be too complicated to implement in the game.
I think it needs a simpler version.
I'm not sure how to simplify this elegantly, as honestly I like it as you presented it, but I'm going to throw some ideas.

First, instead of using lifetimes, let's use a static value, it will be much less confusing, even if it would have made sense to use those.
Second, about the influence of ethics. Why not simply use the approval of the corresponding faction to modify the MTTH ? For example, a spiritualist pop would see its national identity change 25% faster if the spiritualist faction's approval is 75% (or -25% if approval is 25%, though we could double the number).
Finally, related to that, we should use a base MTTH value, which will change with visible modifiers (faction approval, xenophily/xenophoby, strata, citizenship, happiness...).

I think I'm going to ponder on this more, maybe I will provide more complete ideas soon.

 

[nat.hol]

So, I would go with something like this (don't mind the arbitrary numbers ) if we use an acculturation speed:

• Speed base value: 10 (let's say it leads to a MTTH of 50 years)
• from -100% to +100% depending on faction approval
• -100% / -50%/ +50% /+100% from f. xenophobe/xenophobe/xenophile/f. xenophile empire ethic.
• +50% for ruler strata, -20% for worker strata
• -50% to +50% from happiness
• 0% to +50% from proportion of national identity pops on planet
• -20% from Residence, -50% from Slavery, -1000% from Purge

If speed is negative, then the pop may switch to another identity instead, as you mentioned.

Also, I think there should be a penalty for pops of another identity, even with no separatism, like in EU4. The simplest would be decreased happiness.

About separatist rebellions, I think it should depend on stability. Currently, a rebellion can take place with 10 stability or lower. Low stability events occur with 25 or lower, unless there are slaves (then it's 40 or lower). I suggest providing similar events when national identity and stability are low (40 stability, like slave events), which may destabilize further the planet, leading eventually to rebellion if it gets out of hand, or provide an opportunity to let the separatists win without violence.
( https://stellaris.paradoxwikis.com/Planetary_management#Stability )
The main difference with current rebellions would be that the major identity of the planet would decide what becomes of the freed planet. This way, it gets the job done with a minimum number of changes. Also, I disagree with the idea of using the government form to change the way rebellion is handled, though I may change my mind with further explanations.