Can the current tenant stay?
In San Francisco, the answer was more often yes. This is the main moral and empirical case for control.
Rent control, seen from the doorway
The next key
A cap can help a tenant stay home. As a citywide policy, it must also be judged by the homes that remain available, by who can move, and by who can get the next key.
Evidence reviewed · 14 August 2026
One hundred keys represent the rental stock of affected landlords in the San Francisco study. The wall shows a measured result, not a forecast for another city.
Diamond, McQuade and Qian, American Economic Review, 2019Start with the real gain
Protected tenants stayed longer in their homes and in the city.
San Francisco’s expansion reduced the mobility of covered tenants by 20%. The authors also found less displacement from the city. For the person who keeps a home, the protection is concrete: continuity at school, near family, and close to work.
20%
reduction in mobility among covered tenants
Two policy questions
The price of a lease and access to a lease measure different things.
Rent control passes the first test when it slows rent growth in covered homes. An access policy needs three more answers: how many homes remain for rent, how often they become available, and who succeeds in getting them.
Can the next tenant get in?
In the same study, affected landlords reduced rental supply by 15% through sales to owner-occupiers and conversions.
Where the cost moves
A regulated rent becomes help only for the person who gets the home.
When demand exceeds the homes available, selection continues through other means: search time, income stability, deposits, connections, landlord criteria, or a waiting list. The lower price on an existing lease does not show how many people found a lease.
- 01
The cap lowers the covered rent
The gain is concentrated on the tenant who already has access to the home.
- 02
Moving becomes more expensive
The gap between an old rent and the next lease encourages people to stay, even when the home no longer fits their lives.
- 03
Fewer keys return to circulation
Lower mobility slows vacancies. Some rules also lead owners to remove properties from the rental market.
- 04
Other criteria decide who gets in
People who need to move compete for what remains. The cost appears in search, selection, and rents in the unregulated segment.
Where the evidence stops
Rule design and the local market change the result.
A study of Catalonia estimated that its 2020 regulation reduced paid rents by 4% to 6% and found no reduction in rental supply during the period studied. That result does not erase San Francisco. It shows why a universal claim about supply would outrun the evidence.
An evaluation needs all four measures: paid rent, mobility, supply, and access for new tenants. Track only one and you see only part of the effect.
A harder test for a better policy
Protect today’s tenant. Build the path to tomorrow’s lease too.
A good policy says whom it protects and who bears the cost. It must also explain how help reaches people. The four questions below force concrete answers.
- Who receives immediate protection, and who remains outside it?
- What keeps existing homes in the rental market?
- How will supply grow where people want and need to live?
- What targeted help reaches households that do not secure a regulated home?
The OECD synthesis recommends balancing tenant security with affordable rental supply. The tools include targeted allowances, social housing, and land-use rules that permit building where demand grows. Governments can report concrete results: how many households receive support, how many social homes are available, and how many new homes are built.
What to keep
An affordable rent helps only when a key is available too.
Rent control can be powerful insurance for a covered tenant. A policy for the whole city must also answer the person who arrives next.
References
Evidence and limits
The 15-out-of-100 figure describes San Francisco’s 1994 expansion. The studies cover different rules, periods, and markets. This page does not transfer one result mechanically to another country.
Effects on tenants, landlords, and inequality
The San Francisco natural experiment: 20% lower mobility and 15% lower rental supply in the affected group.
DOIAn almost complete review of empirical research
Surveys recurring results and the differences between forms of rent control.
DOINew evidence from Catalonia
Found paid rents 4% to 6% lower and no rental-stock reduction in the observation window.
DOIHousing allocation under rent control
Shows empirically that a shortage can allocate homes poorly across households even when prices are regulated.
DOIBrick by Brick
Policy synthesis on tenant protection, allowances, social housing, and supply constrained by land-use rules.
DOI
The figures come directly from the cited studies. "The next key" connects access with mobility and supply. The policy questions offer a way to judge the effects. Evidence reviewed 14 August 2026.