The Geographic Determinants of Housing Supply

Summary

"The Geographic Determinants of Housing Supply" is an article by Albert Saiz, published in the Quarterly Journal of Economics, volume 125, issue 3 (2010), pages 1253–1296 (DOI: 10.1162/qjec.2010.125.3.1253). Saiz wrote the paper as an assistant professor of real estate and economics at the Wharton School, University of Pennsylvania; he later moved to MIT, where he is now the Daniel Rose Associate Professor of Urban Economics and Real Estate and directs the MIT Urban Economics Lab. The paper is one of the most cited in modern urban and housing economics (well over a thousand citations), and its central contribution — a metropolitan-area-level measure of physically developable land, built from satellite elevation and water-body data — has become a standard instrument in subsequent housing-supply and house-price research. The paper is not about land value taxation and does not propose or evaluate one. It is included on this wiki because it is the leading empirical account of why housing supply is elastic in some US metropolitan areas and inelastic in others — a question that bears directly, but indirectly, on whether land value capture translates into cheaper housing (see "Relation to the Georgist Case" below).

The Core Argument and Findings

1. A new, geography-based measure of developable land. Saiz processes satellite-generated data on terrain elevation and the presence of water bodies (oceans, lakes, wetlands, rivers) within a fixed radius (approximately 50 kilometers/circa 32 miles) of each of 269 US metropolitan-area centers, to construct an index of the share of land that is unavailable for development because it is underwater or on slopes too steep (in Saiz's construction, above roughly a 15-degree grade) to build on economically. This produces a consistent, exogenous, city-by-city measure of physical land scarcity that does not depend on self-reported or survey-based data.
2. Physical geography strongly predicts low housing-supply elasticity. Saiz finds that metropolitan areas most often cited in the literature as having inelastic housing supply — for example coastal and land-constrained markets — are, empirically, also the metro areas most severely constrained by unavailable land under his satellite-derived measure. Areas with abundant flat, dry, developable land (concentrated in the US Midwest and interior South) show markedly higher estimated supply elasticities; areas with severe land constraints (much of coastal California, the New York City area, South Florida) show markedly lower ones. Supply elasticities in the paper vary dramatically across metro areas, from below 1 in the most land-constrained coastal markets to above 3 in the least constrained inland ones; Saiz's estimate for the San Francisco metro area, for instance, is on the order of 0.6–0.7 [VERIFY: exact reported value and its precise definition (long-run price elasticity of housing supply) — corroborated across multiple independent secondary summaries but not confirmed against a directly fetched copy of the published tables in this session].
3. Regulation and geography are jointly determining, and geography matters more as cities grow. Econometrically, Saiz models supply elasticity as a function of both physical land unavailability and local land-use regulatory stringency (using regulatory-index data from companion work, including the Wharton Residential Land Use Regulatory Index co-developed by Saiz with Joseph Gyourko and Anita Summers). The two are not independent: Saiz finds that regulation is itself, in part, an outcome of geography and demand — land-scarce, high-demand places are also where local governments have adopted the strictest land-use regulation, consistent with the "homevoter" pattern in which existing landowners in tightly constrained, high-value markets support restricting new supply. As a city's population grows, the physical land-unavailability constraint becomes an increasingly binding determinant of its supply elasticity relative to regulation alone.
4. Constrained supply raises prices, primarily via the price of land. Because both physical and regulatory constraints restrict how much new housing can be built in response to demand, cities with low estimated elasticities see demand shocks (income growth, in-migration) converted disproportionately into higher prices rather than more construction. Saiz's framework and its empirical grounding is the standard modern citation for the claim that persistently high house prices in supply-constrained US metros are substantially a land-scarcity phenomenon — not merely a construction-cost phenomenon — since it is the land input, not the reproducible structure, that is fixed by geography and restricted by regulation.

Relation to the Georgist Case

Saiz's paper supports the land-scarcity mechanism that motivates the Georgist case for housing affordability, but it is not itself an argument for land value taxation, and this wiki should not present it as one:

• What it supports. The paper is rigorous, independently derived, mainstream evidence for the proposition that where new housing cannot be built — because land is physically scarce, tightly regulated, or both — rising demand shows up as higher land and house prices rather than more supply. This is the same land-scarcity logic behind the Georgist claim that unrestricted land rent, not the cost of producing housing structures, drives high housing costs in supply-constrained cities. It is consistent with, and complements, the long-run price evidence in Knoll, Schularick & Steger (2017), which finds that the post-1950 rise in real house prices across 14 advanced economies is overwhelmingly a land-price phenomenon rather than a construction-cost phenomenon, and with the labor-misallocation channel modeled in Hsieh & Moretti (2019), who use housing-supply constraints in high-productivity cities (closely related to Saiz-style elasticity measures) to estimate a national output cost of restricted supply.
• What it does not show. Saiz's paper makes no claim about land value taxation, land value capture, or any tax-policy instrument. It does not test whether an LVT would ease supply constraints, and its regulatory-constraint findings point toward land-use liberalization (zoning and permitting reform), not tax policy, as the direct lever on the supply side. The paper's geographic constraint (terrain, water) is, by construction, not something any tax policy can change; only the regulatory component of its story is policy-tractable at all, and Saiz's own point is that the regulatory component interacts with, rather than substitutes for, physical geography.
• How it bears on the affordability outcome. This wiki's lvt-improves-housing-affordability outcome page already argues that LVT eases housing costs mainly by discouraging speculative underuse of urban land and encouraging development on land already zoned for it — but that this supply effect only translates into affordability where permissive land-use policy allows construction to respond. Saiz's paper supplies the underlying empirical account of exactly why that "permissive land-use policy" caveat is doing so much work: in a large share of US metro areas, the binding constraint on new supply is not landowner behavior that an LVT would change, but a mix of immovable physical geography and regulatory choices that are logically and politically separate from the tax base. Saiz's evidence therefore supports the land-scarcity half of the affordability story (land, not structures, is what is scarce and expensive) without supporting the causal claim that taxing land value would relax the supply constraint — that latter claim depends on complementary zoning reform, a distinct policy lever this paper does not evaluate.

Nuances and Limits

• Not a study of land value taxation. As emphasized above, the paper contains no discussion of LVT, split-rate taxation, or land value capture; any connection to Georgist policy is drawn by this wiki and other secondary work, not asserted by Saiz.
• Elasticity estimates are model-based, not natural-experiment estimates. The supply elasticities are derived from a structural econometric model relating house-price growth and construction to Saiz's land-availability index and regulatory measures, under identifying assumptions about housing demand and supply. As with any such model, the precise numerical elasticities are sensitive to specification choices, though the qualitative ranking of metro areas (land-constrained coastal markets as consistently less elastic than land-abundant interior markets) is considered a robust and widely replicated finding in the subsequent literature.
• Regulation is partly endogenous. Saiz's own finding that stricter regulation clusters in already land-scarce, high-value markets means that his estimates cannot cleanly separate "pure" geographic scarcity from regulatory choices that are themselves a political response to scarcity and rising prices — a point later work (including Saiz's own subsequent papers) has continued to refine.
• US-specific and cross-sectional. The paper's 269-metro sample and satellite-derived measure are specific to the US; the paper does not test whether the same geography/regulation interaction holds cross-nationally, though the general logic (fixed land supply plus endogenous local regulation) has been applied elsewhere in later research.
• Silent on land value assessment or capture. The paper offers no evidence on whether or how governments could capture the land-value gains it documents, nor on the administrability of doing so — a separate question addressed elsewhere on this wiki (e.g. land cannot be assessed).

Bears On

• Outcome: LVT improves housing affordability — supplies the leading empirical account of why housing supply is inelastic in many high-demand US cities (physical land scarcity compounded by regulation), grounding this wiki's caveat that LVT's affordability effect depends on complementary, permissive land-use policy rather than tax design alone.
• Research: Knoll, Schularick & Steger (2017), No Price Like Home — independently corroborates, over 140 years and 14 countries, that land price (not construction cost) drives long-run house-price growth; Saiz supplies the metro-level, cross-sectional mechanism (geography plus regulation) for the same land-scarcity story.
• Research: Hsieh & Moretti (2019), Housing Constraints and Spatial Misallocation — models the aggregate output cost of the same kind of supply-constrained, high-demand cities that Saiz's elasticity measure identifies.
• Concept: Land Value Tax — Saiz's findings sharpen the scope condition on affordability claims made for LVT: land scarcity, not necessarily land-holding behavior, is often the binding constraint.

See Also

• Glaeser & Gyourko (2018), The Economic Implications of Housing Supply
• Housing Constraints and Spatial Misallocation (Hsieh & Moretti 2019)
• No Price Like Home: Global House Prices, 1870–2012 (Knoll, Schularick & Steger 2017)
• Land Value Tax
• Land Value Capture
• Objection: Land value can't be assessed accurately

Sources

1. Albert Saiz (2010), "The Geographic Determinants of Housing Supply," Quarterly Journal of Economics, 125(3): 1253–1296. DOI: 10.1162/qjec.2010.125.3.1253 · IDEAS/RePEc listing — used for bibliographic details, the satellite-derived land-unavailability methodology, the 269-metro sample, and the core finding that geography and regulation jointly determine housing-supply elasticity. This session's proxied web access could not directly retrieve the AEA/Oxford Academic full text or PDF mirrors (network errors/403s), so specific elasticity figures are drawn from multiple independently agreeing secondary summaries and are flagged [VERIFY] where precision matters.
2. Joseph Gyourko, Albert Saiz & Anita A. Summers (2008), "A New Measure of the Local Regulatory Environment for Housing Markets: The Wharton Residential Land Use Regulatory Index," Urban Studies 45(3). SSRN — used for the companion regulatory index Saiz (2010) draws on to separate physical from regulatory constraints.
3. MIT Center for Real Estate / Urban Economics Lab, faculty profile of Albert Saiz. MIT CRE — used for Saiz's career trajectory (Wharton at time of publication, later MIT) and current title.
4. "Geographic Determinants of Housing Supply, A. Saiz (2010)," A Fine Theorem (blog review). afinetheorem.wordpress.com — used as a secondary corroborating summary of the paper's geography/regulation/homevoter findings.

[CITATION NEEDED: a directly fetched copy of the published QJE tables confirming the precise San Francisco elasticity estimate, the exact interquartile-range elasticity comparison, and the full 269-MSA figure, since this session's egress proxy returned errors or 403s for academic.oup.com, fpeckert.me, real.wharton.upenn.edu, and other PDF mirrors of the paper. The qualitative findings above (geography and regulation jointly constrain supply; land-constrained coastal metros are systematically less elastic) are corroborated across multiple independent, mutually agreeing secondary sources and are treated as reliable; the specific numeric elasticity values should be confirmed against primary tables by a future editor with working access.]