Perhaps this was mentioned before... The concept of population migration between cities is missing from the game, unless I'm missing something. I suppose it was left out to keep the challenge of growing cities on less fertile sites, which is a gameplay reason but not realistic. Suppose we have an infertile site with a luxury resource, such as gold. History shows that a massive migration will take place, such as the California gold rush. Even if there's no reason for voluntary migration, forced relocations took place worldwide until most recent times. I don't think that allowing a settler to join a city would be appropriate. As I see it, the settler is not just 1 population but also includes all the resources needed for founding a city. Another argument is that both the settler and worker don't subtract population, so they shouldn't add any. So I propose a new unit: the migrant costing 1 population. Real migrants don't have resources, so the migrant should cost just a few hammers. Real migrants are also unhappy, so I'd make the migrant unhappy upon joining a city for X turns, so a city would gain one temporarily unhappy citizen. This one unhappiness could also be interpreted in another way: the immigrants cause temporary unrest among the city population until they are assimilated. You could relocate angry citizens, giving you another way of dealing with overpopulation. You might reconsider your preferred site for expansion. Colonization would be way more dynamic. The ability to move populations would be quite a power trip, which is what Civ is all about. Thanks for considering!