The important caveat
Strong evidenceLegal on paper is not the same as buildable in practice.
A reform can promise density and still bury it under tiny maps, parking ratios, setbacks, fees, hearings, and delay. Good reform makes ordinary projects legal, feasible, and predictable.
Figures from the papers
Inspect the published evidence directly
Figure 2 · Living space after upzoning
The strongest post-reform increases appear after roughly five years, especially for large upzonings.
Figure 6 · Estimated treatment effects on dwelling permits
The estimated effects become positive after the reform for both attached and detached homes.
Figure 2 · Average number of addresses before and after reform
The two groups track similarly before reform and separate gradually afterward.
Figure 3 · Cumulative residential units permitted
Chicago's cumulative permit paths changed unevenly across neighborhoods and rule types.
Evidence stack
Studies behind this conclusion
Upzoning Chicago
Narrow transit-area upzonings raised affected property values but did not produce detectable additional housing during the five-year study window.
Keep in mind: A localized reform and limited horizon may behave differently from broad reform.
Study details →Does Zoning Help or Hinder Transit-Oriented (Re)development?
Transit-supportive zoning helped create development opportunities, but market demand, parcel conditions, public investment, and political support determined whether projects followed.
Keep in mind: Six station-area case studies reveal implementation mechanisms but do not identify an average causal effect of zoning.
Study details →Jumpstarting the Market for Accessory Dwelling Units
ADU production depended on a bundle of usable zoning, flexible occupancy and parking rules, manageable fees, financing, and technical help.
Portland issued nearly 2,000 ADU permits after 2010
Keep in mind: The study is descriptive: policy, demand, and homeowner selection changed together, so the permit count is not a causal estimate.
Study details →Not So Gentle Density: An Early Assessment of the San Diego Bonus ADU Program
The bonus program enabled small multifamily-style infill, but utility costs, financing, geography, and implementation capacity constrained early delivery.
40% of proposed bonus ADUs were in Moderate Resource areas, versus 25% of all ADUs
Keep in mind: Most observations were proposed or permitted rather than completed; overlapping state and local reforms prevent a citywide causal conclusion.
Study details →Making Housing Affordable? The Local Effects of Relaxing Land-Use Regulation
Substantial upzonings increased housing over five to ten years, especially where prior zoning was binding and rents signaled strong demand.
About 9% more living space and housing units in upzoned areas after five to ten years
Keep in mind: Local quality-adjusted rents did not differ significantly from later-upzoned controls; effects may diffuse across the wider market, and the setting is one Swiss canton.
Study details →The Impact of Upzoning on Housing Construction in Auckland
A broad reform covering roughly three quarters of residential land produced a large increase in permitted homes relative to non-upzoned areas.
21,808 additional permitted homes over five years
Keep in mind: Permits are not the same as completed or net new occupied homes.
Study details →Land-Use Reforms and Housing Costs
Loosening reforms were followed by modest average supply gains, while tightening reforms reduced middle-income-affordable units and raised rents.
Loosening was associated with 0.8% more housing after 3–9 years
Keep in mind: Reforms are heterogeneous and the cross-city design remains observational.
Study details →From evidence to policy