Immigration
Every day, a small number of families and single adults arrive at your city’s edge looking for a place to live. This page explains how they get picked, where they end up, and why your population’s age, wealth, and education look the way they do.
The bouncer
Microlandia handles who moves in the way real housing markets do, with a bouncer at the door. Each day the city rolls (that is, randomly samples) an applicant from a realistic distribution of would-be arrivals, with their education, age, savings, and income drawn together so they make sense as a single person. The bouncer then checks whether that applicant qualifies for the vacancy in front of them. If they pass, they move in. If they fail, the bouncer re-rolls a fresh applicant and tries again.
The reason the bouncer exists is survivorship bias. If we just spawned a new resident straight into each empty unit, every move-in would look perfectly matched to their building by definition. No other candidate was ever considered, and no one was ever turned away.
The bouncer makes rejection visible. A premium townhouse can sit empty for weeks not because nobody wanted it, but because the kind of person who wanted it could not show up with three months of rent. Empty units are real signal about which applicants the door turned away, not just noise.
The daily flow
Once per day the city runs an immigration tick:
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Decide how many people will try today. Culture buildings, like museums, film studios, and music clubs, are how the outside world hears about your city. The more culture you have, the more applicants will try their luck each day. A
cultural_boomevent doubles the count while it lasts. -
Pick a building to fill. Every home that has a free unit is sorted by neighborhood quality, best first. The day’s applicants are pointed at these vacancies in that order.
- Roll a coherent applicant. The city samples one person at a time, in this order:
- Education. Most arrivals have at least a high school diploma. A large minority hold a college degree. A smaller share have no diploma at all.
- Profession. Degree-holders get a specialist role like engineer, doctor, or lawyer. The rest get an unspecialized job, or no job at all.
- Age. Uniformly random across working age, from when school ends to the retirement age.
- Savings. Drawn from a savings ladder that varies by generation. Older people skew richer because they have had more years to save.
- Income. The monthly income they would earn given that profession and degree status.
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Check the door. Every applicant has to pass two gates:
- Affordability. The bar is three months of rent in ready cash. Ready cash means current savings plus one month of expected income. Real landlords accept a paycheck stub next to a savings statement, and the door follows the same rule. A young earner with a thin balance still qualifies if a paycheck is on the way. An unemployed person with low savings does not.
- Class match. This rule only fires at one tier. High-net-worth applicants demand premium housing in top-quality neighborhoods, and they will refuse anything else at the door. Their downstream behavior, including how they react to crime, how they spend money, and which transport they pick, all assumes they live in the premium tier. Everyone else, regardless of class, can take any tier they can afford.
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Re-roll a few times. If the first applicant fails either gate, the door rolls a new one. After up to eight tries the slot stays empty for the day and waits for tomorrow.
- Where people end up. Most of the sorting between rich and poor neighborhoods happens through rent alone. A premium townhouse with a steep rent prices out anyone whose savings plus paycheck cannot cover three months upfront, no matter their class. The class rule is one extra filter on top, but only at the premium tier.
Family
A small share of arrivals come as families. The family pack is a spouse plus zero to two children. The spouse is rolled with the same education, age, and savings odds, independent of the first applicant. The whole household moves in or moves on as a unit.
If the family has school-age children, your city has to have open school seats for them. Otherwise the family does not move in. There is one exception. If your city has zero schools and both parents are themselves unschooled, the family is admitted and the children grow up unschooled. This keeps unschooled families from being permanently locked out of unschooled cities.
Why your city looks the way it does
A few patterns this system produces, and what they mean for you:
“Why are my buildings not filling up?” The daily attempt count is gated by your culture buildings. With one museum the trickle is slow, and clearing a big vacancy backlog takes years at that rate. Build culture if you want to grow. It is the strongest growth lever you have.
“Who lives in my premium district?” A mix. The few high-net-worth applicants the door admits, plus anyone else who can afford the rent. High-net-worth citizens skew older, because that kind of wealth is mostly years of saving. A top-paid doctor or executive can qualify on income, but the savings path is the more common one. Below the premium tier, your neighborhood is whoever can cover three months of rent.
“Why so many people without a diploma?” A meaningful share of adult arrivals are unschooled by design, calibrated to real immigration data. On top of that, city-born children who age past school age without a seat also graduate as unschooled. If you do not build enough schools, your own kids drop out. Both groups end up earning the minimum wage, which is why the bottom of the salary chart can look like one large low-skill cluster.
“Why is basic-tier housing empty next to homeless people?” The label “basic” refers to building quality, not price. A basic unit in a desirable area can still cost more than a standard unit in a poor one. And most homeless citizens have negative bank balances. They could not afford a $1 per month unit, let alone three months of rent upfront. Shelters, not the immigration door, are how homeless people find a roof.
Player levers
If you want to shape who moves in:
- Build culture buildings. More attempts per day means more move-ins.
- Build schools before your kids age out. Otherwise the next generation joins the unschooled cluster.
- Mix housing tiers. All-premium gives you an aging, expensive-to-fill district. All-basic gives you no upper-income tax base.
- Set rent intentionally. A higher rent excludes lower-income applicants at the door. A lower rent broadens the pool. Neighborhood quality drives the rent your buildings can sustain, but the door itself only enforces a class bar at the premium tier.
- Homeless need shelters, or housing priced for their wallet. The immigration door will not admit anyone who cannot cover three months upfront.
Parameters
Family ratio
0.08
Probability that an immigrant arrives with family (spouse plus 0-2 children).
Bachelors degree ratio
0.48
Ratio of immigrants arriving with a bachelor’s degree or higher.
High school ratio
0.72
Among immigrants without a bachelor’s degree, the ratio who have at least a high school diploma.