One thing that is an issue with Revolutions that is affecting this is the impact of Life Ratings on Population Growth.
Because the AI will not attack areas where there are large concentration of <30 LR provinces, for Revoltions a "floor" was created for LR at 30, with a few isolated 25 LR provinces, for the world once settled (unclaimed colonies start lower, and once claimed have events fire to raise their LR to 25-30 range).
If you don't have this, AI nations will end up in never ending colonial wars, as for example ENG AI will not attack holdings in the mid-Sahara due to the impact of low LR provinces on military attrition, but the French who own them won't admit defeat because it still has a colonial base. End up with colonial wars that last decades. After first trying, and failing, to fix the problem with boosts to attrition reduction to see if that would make the AI more willing to attack low-LR provinces, the only real alternative was to set a base LR. And while colonial war standoffs still can happen in Revolutions, it is less problematic now than it was in earlier versions.
So what does this have to do with population in Europe?
If the "floor" LR in deepest Africa is 25-30, provinces in Europe should have of course on average higher LRs. This means that Western Europe, Eastern North America, California, SE Australia & New Zealand, and parts of China and Japan are usually 40 LR, with some areas of high development 45-50. Unfortunately, the impact of these higher LR base provinces, combined with inventions that raise POP growth rates further, result in population growth that in the end is too high for Europe.
Interestingly though, while the POP rates are too high in Europe, in the colonial empires the POP rate is still too low. Places like Ceylon or Senegal will still be underpopulated, even when accounting for lack of migration, by 1935 while Britain and France will be overpopulated. This is because another impact for determining POP is ability to meet daily needs, which is tied to income. Since colonial POPs almost always are non-National, their ability to fill needs is less, so lower POP growth results that is compounded by living in lower LR provinces.
And then there are other factors - having good social reforms, esp health care, also appears to raise POP growth rates from what I can tell. And the more I test, the more I'm convinced that there is a difference between civilized and uncivilized, all other things being equal.
So what is the solution? If you cut the base growth rates, you risk making colonial areas have negative POP growth, when in fact from the start they should have positive POP growth (test this with France - put the beginning POP growth rate and colonies like the West Indies will have slightly negative POP growth, even while the mainland French provinces will have lower, but still positive, POP growth.)
One thing I am testing with VIP for a future release is to model the impact of what demographers call the Demographic Transition. Population growth rates in the industrialized West rose (except in France) so that there was very high population growth - ENG and GER in particular. After 1900 there was a shift, as the change from an agricultural to industrial society led to rapid declines in birthrates, so that countries like ENG and GER began to have pop growth rates more like France in the 19th C with slow, moderate population growth. In VIP what I'm testing is having the event take away the POP growth bonuses gained from earlier inventions, plus a bit more to balance out for the impact of better health care reforms and the like.
But this isn't an optimal solution, because while Europe experienced this transition, it's colonial holdings did not, and in fact population growth in colonial areas was very strong and rising after 1900, not moving toward steady-state. So there are problems with trying to model the demographic transition for a nation as a whole if that nation has a colonial empire.
In the end, Victoria is not a historical simulator, and it will be almost impossible to get populations to be exactly as they historically were. In general, the balance of populations for 1836 is quite close to correct for most areas, so that while the overall numbers by the end may be off, the general balance between the major nations/empires should still be somewhat close.
This is definitely one of the issues I'm working on to try and improve for the future. The biggest problem is that there are several factors combinig to make finding an easy balance difficult. And in the end, the difference between an LR 30 province and an LR 40 province turn out to be quite significant in terms of their impact on POP growth.
