Technically, no one is leaving or coming into the city. Population growth is stagnant. Sims don’t need to travel long distances, because their workplace is just within walking distance. In fact they do not even need to leave their own block... Suffocating air pollution, high unemployment, no fire stations, schools, or hospitals, a regimented lifestyle - this is the price that these sims pay for living in the city with the highest population. It’s a sick and twisted goal to strive towards. The ironic thing about it is the sims in Magnasanti tolerate it. They don’t rebel, or cause revolutions and social chaos. No one considers challenging the system by physical means since a hyper-efficient police state keeps them in line. They have all been successfully dumbed down, sickened with poor health, enslaved and mind-controlled just enough to keep this system going for thousands of years...
In the video at 6:39, you can see that the population precipitously dies off after age 60. And, in case you were wondering, the creator says "I am not autistic, or a savant, nor suffer from OCD, or suffer from any other form of clinical mental disease or illness for that matter."
http://www.viceland.com/blogs/uk-games/2010/05/10/the-totalitarian-buddhist-who-beat-sim-city/.
To get this far and to dive that deep into it... Pretty amazing.
It sortof reminds me of a city that would be in "Brave New World", an engineered police state with total control of it's citizens. Most of that video weirded me out, all the small details that guy had to comprehend about the whole game.
Wellllll...Stalin would be proud. :-/