The Lot Size Lock: Single-Family Zoning and the Geography of Staying Put

Reframing the Dependent Variable

Housing research has traditionally measured zoning's harms through prices: how much does a regulation cost, how much does it constrain supply? But a growing body of peer-reviewed work suggests the more consequential outcome is not the price of housing but the stuckness of people. When minimum lot sizes, bans on multifamily construction, and parking mandates make it illegal to build modest apartments in opportunity-dense neighborhoods, low-income renters are not merely paying more — they are being confined. This review examines how researchers can operationalize that confinement, and why the measurement choices we make determine whether zoning reform is treated as a consumer issue or a rights issue.

The Empirical Consensus on Exclusionary Effects

The literature is unusually consistent for a contested policy domain. Studies of metropolitan land-use regimes — including influential work by Glaeser and Gyourko on regulatory tax, Lens and Monkkonen on segregation outcomes, and Rothwell and Massey on the geography of educational opportunity — converge on a central finding: metros with restrictive single-family zoning exhibit higher housing costs, lower interneighborhood mobility for poor households, and greater racialized separation. The mechanism is straightforward. When a metro's high-opportunity neighborhoods are zoned exclusively for large-lot single-family homes, the only housing affordable to low-income renters is concentrated in a residual set of neighborhoods, often with weaker schools, longer commutes, and thinner labor markets.

Crucially, this is immobility in both senses of the word. Households cannot move in to opportunity, and having been sorted, they cannot easily move out of disadvantage. Transportation research reinforces the point: dispersed, peripheral affordable housing raises per-household vehicle dependence, and the resulting cost burden further constrains residential choice.

Toward a Measurement Framework: An Immobility Index

We propose that researchers and policymakers evaluate metropolitan areas on a composite immobility index with four components, each drawn from established methodological practice:

1. Regulatory restrictiveness. Share of residential land zoned exclusively for single-family use, derived from parcel-level zoning GIS data in the tradition of the Urban Institute's and Pew's land-use audits.
2. Minimum lot size burden. Median minimum lot area in high-opportunity census tracts, standardized against tract-level median income.
3. Spatial opportunity mismatch. The dissimilarity index between where income-restricted renter households can afford housing and where job-access and school-quality metrics peak.
4. Observed mobility differential. The gap in inter-neighborhood migration rates between low-income and high-income renter households, estimated from IRS Statistics of Income migration files or ACS linked samples.

Applying this framework qualitatively to the current landscape, the metros most likely to score as most mobility-restrictive include the usual suspects identified in prior land-use research: the San Francisco Bay Area, Los Angeles, New York, Boston, Seattle, San Diego, Washington D.C., Denver, Portland, and Austin — all places where opportunity-dense cores are ringed by vast tracts of legally protected single-family land. The ranking's value lies less in ordinal precision than in making visible the regulatory architecture that produces it.

Methodological Cautions

Three caveats deserve emphasis. First, zoning is endogenous: affluent residents seek restrictive rules, so causal identification requires quasi-experimental designs — boundary discontinuities at jurisdictional lines, or natural experiments such as Minneapolis's 2019 elimination of single-family-only zoning and California's SB 9 — rather than naive cross-metro correlations. Second, land-use data are fragmented across thousands of municipalities; any national index must disclose its imputation and harmonization decisions. Third, deregulation alone is not a guarantee of inclusive outcomes; without complementary protections, upzoning can accelerate speculative turnover. Research designs should therefore track displacement alongside access.

Why Methodology Is a Rights Question

How scholars measure a harm shapes how institutions respond to it. So long as zoning's effects are captured solely as price elasticities, reform will remain a debate among economists. When those effects are measured as restricted spatial freedom — the measurable inability of a household to live where opportunity concentrates — the analysis enters the domain of human rights, where freedom of movement and equal access to the conditions of flourishing are the governing standards. The methods described here are a step toward making that framing empirically defensible, and toward holding metropolitan governments accountable for the immobility their zoning codes quietly produce.