In the early days of my galaxy, there were 6 different races. Each of us would generate, for our own civilizations, one Galactic Citizen each 10 turns.
One day, about 2 years into our exploration, the gruff and hungry Drengin leader declared War on my entire race. Until that point, my only interaction with him was when one of my trade freighters had crossed path with a small scout ship from the then Drengin Colonies at the far North of our galaxy. The captain of the freighter reported a mild concern not that the captain of the scout ship had expressed hunger, but how he expressed it.
But the Drengin were so far away and our people were busy colonizing, mining, and learning all we could about our part of the galaxy.
About a year later, the Altarians declared War on us, even before greeting us.
For the next 7 years, the Terran Alliance prosecuted the "War of the Existentials", mostly fighting the Altarians and taking planet after planet and system after system, while simultaneously building our defenses against the Drengin. Finally, the beautiful-though-in-need-of-a-day-in-the-sun Altarian leader proposed a Peace Treaty. Our leadership agreed, and we moved our navies Northwestward, to confront the growing Drengin threat, with which we were technically still at War. A few scant weeks later, the Altarian Resistance fell, either by collapsing from the rot within, or by having its last world conquered by another race sharing our galaxy.
After about a year of fighting the Drengin, they suddenly surrendered all of their assets to us, ending that war too.
TL/DR:
We started with 3 races, each generating a Galactic Citizen every 10 turns.
One race (mine) conquers an entire civilization, and 90%+ of another. Through a combination of organic growth and conquest (though we never declared War or antagonized any other civilization to the brink of War), the Terran Alliance is now 3 to 4 times LARGER than it was, with much greater diversity in DNA, education systems, manufacturing, trade, and resource production. In fact, we are so diverse that humans only make up about a third of the entire population now.
Question: Why does such a huge and diverse population only generate ONE Galactic Citizen every 10 turns, and not at least the three that the original three civilizations generated?
Conclusion: This example is given in light of conquest, but I still feel that the production of Galactic Citizens needs to be reassessed in light of how communities and civilizations actually work as they grow, especially if governance works smoothly and education systems are functioning correctly. I think it's appropriate to consider some form of "scaling up" as a civilization grows. Maybe not in a straight-line, due to the bureaucratic and administrative costs of bigger and bigger organizations, but some scaling factor should be considered.