Migration Flow
People move to your city for work, as many a day as its culture draws.
The door in
Culture sets the cap. Each culture point lets one newcomer arrive a day. City Hall carries one point, so every city grows a little from day one. The squares, the sanctuary, the museums, the library, the planetarium and the chess club add one each; the techno club adds two. A cultural boom doubles your culture while it lasts.
Jobs come first. Each of the day’s places goes to your best-paying open job: someone of that trade moves in to take it, and a partner takes another open job that fits them. Your residents get a week to fill a posting before newcomers can. When no open job is left, about one place in ten is still taken by someone coming to look for work. If they have found none after a month, they go back home.
Newcomers are mostly young adults, especially ages 20 to 34, and their age shapes the savings they bring. Each one tries the best vacant home first; a household that cannot rent it turns back, and the place stays empty until tomorrow.
The lease screen. A household qualifies with after-tax monthly income of at least 3× the rent, or six months of rent in savings. Both spouses count, but only actual offers, pensions and basic income qualify as income. Hoping to find work is not proof of earnings. Two adults need two separate offers to count two salaries.
A small share of applicants who fail the lease screen still come. They take free shelter beds when available; only rarely do they arrive without housing. Shelters therefore help newcomers as well as residents who lose their homes. Children enrol where school seats are available, and a promised job starts only if its commute works. A family can arrive before a classroom is available.
The door out
Once a month, each household weighs a move. Nobody leaves without a reason your city gave them: high taxes, rent it can no longer afford, no school place for the children, crime, a long hospital wait, unmet maternity care, no electricity or unaffordable driving fees. The strongest problem it faced that month is the one that counts. Losing a job is not a reason to leave: the jobless stay and look for work while their savings last.
Young adults, renters and degree holders move more often. Children in school and older age make a household less mobile. Every income class can leave, but a move needs $1,000 in household cash. A household that cannot pay stays, even when its problems are severe.
Newcomers who came looking for work and have none after a month go back home, during their first two years. That trip needs only a $100 return fare. Households formed by residents already living here do not count as newcomers. Most households stay each month; complaints do not cause an immediate departure.
A departing employee leaves a job posting for a replacement. The census records the household’s strongest reason, its income class and whether each departing person was employed.
If a family falls two months behind on rent, they lose their home but stay in your city, waiting for an affordable home or a place in a shelter. Without a home, citizens are more likely to get sick and face an employment barrier. The barrier is drawn once per jobless spell, so more vacancies or another day do not reroll it. Moving into a home or shelter removes it. You can help them recover by providing shelters and homes they can afford. Keep that in mind before you bulldoze an occupied building: its residents will need somewhere to go, just as they would after a fire.
Flowing through
This push and pull is the spine of Everett Lee’s A Theory of Migration, a 1966 paper that still shapes how demographers think about who moves and why.
Your city is the destination, the wider world the origin, and your city’s economic, social, political and environmental conditions are the obstacles between.
| Pushes people away | Draws them in | |
|---|---|---|
| Economic | High taxes, rent too high, no job found | Open jobs to fill |
| Social | No classroom for the kids, crime | Culture |
Player levers
- Build culture to raise the cap. Every culture point lets one more newcomer arrive each day.
- Open jobs to fill it. Newcomers come for the jobs your residents leave open, so a workplace short of a trade brings people of that trade.
- Build schools before families arrive. Families may move in before places are available, leaving children waiting for enrolment.
- Keep somewhere cheaper to land. Vacancy is the release valve: with nothing open to downsize into, a priced-out household has more reason to leave instead of moving across town.
Parameters
Family ratio
0.08
Probability that an immigrant arrives with family (spouse plus 0-2 children).
Bachelors degree ratio
0.48
Share of arrivals who show up with a bachelor’s degree or higher. Whether they actually work as professionals depends on the workplaces you build; otherwise they move in and take lower work.
High school ratio
0.72
Among immigrants without a bachelor’s degree, the ratio who have at least a high school diploma.
Movers by age
The ages of the adults who move in. Most are in their twenties and early thirties, so a growing city soon needs schools, and one that stops growing slowly grows old.
| Key | Value (thousands) |
|---|---|
| Age 18 to 19 | 339 |
| Age 20 to 24 | 1855 |
| Age 25 to 29 | 1870 |
| Age 30 to 34 | 1236 |
| Age 35 to 39 | 877 |
| Age 40 to 44 | 535 |
| Age 45 to 49 | 534 |
| Age 50 to 54 | 491 |
| Age 55 to 59 | 493 |
| Age 60 to 64 | 474 |
| Age 65 to 74 | 518 |
| Age 75 plus | 329 |
Basis: measured
Source: U.S. Census Bureau, Geographic Mobility: 2023 (CPS), table 1
Immigrant commute quarantine days
30
How long a posting stops pulling immigrants after an arrival who claimed it turned out to be unable to commute there. Only the door is closed: locals still see and can take the posting through employmentSearch.
⚠️ Source pending