An urban growth boundary (UGB) is a regulatory line intended to contain urban sprawl by restricting urban development to land inside it. Mathur (2014, Housing Studies) estimated that the UGB in King County, Washington raised vacant-land prices by about 230 percent while slightly lowering single-family house prices (about -1.3 percent), and interpreted the near-zero net house-price effect as the land-supply restriction being offset by supply-expanding policies adopted alongside the boundary, such as minimum density requirements, multifamily zoning, and accessory dwelling unit ordinances. Whether that interpretation is correct is unknown: the net effect has never been decomposed into its channels. The open problem is to identify what actually drives the net housing-price effect of the UGB regime: the boundary's land-supply restriction, the gradual capitalization of UGB benefits (cost savings, natural-resource preservation, economic efficiency) into prices as the housing market matures, homebuyer preferences for locations inside versus outside the boundary, and the individual and joint contributions of the supporting policies. No existing study decomposes this net effect for King County or for a comparable UGB case, so the problem remains open.

Background

An urban growth boundary (UGB) is a legally drawn line around an urbanized area outside of which urban-scale development is generally prohibited; it is the central containment instrument of growth-management programs such as Washington State's Growth Management Act (adopted 1990), under which King County (the Seattle metropolitan core) designated its UGB in the mid-1990s. UGBs are motivated by goals such as farmland and natural-resource protection, infrastructure cost savings, and more compact urban form. Their housing-market consequences are theoretically ambiguous: restricting the land supply should raise land and (other things equal) house prices, while any amenity benefits the boundary generates should be capitalized into prices (that is, durably reflected in what buyers pay for homes), and supply-expanding regulations inside the boundary should push house prices down. Whether a UGB raises or lowers housing costs therefore depends on the balance of these channels.

The standard empirical tool is the hedonic price model, in which the price of a house is regressed on its characteristics and its location relative to the boundary; spatial econometric variants correct for correlation between nearby transactions. Mathur (2014) applied a two-stage spatial hedonic design to sales of single-family homes and vacant single-family lots within two miles of either side of the eastern boundary of King County's primary UGB (transactions during the study period around 2004-2006, per the study record). The headline results were strikingly asymmetric: land prices roughly 230 percent higher attributable to the UGB, but house prices about 1.3 percent lower. Because land is only one input into housing production, the author attributed the muted house-price response to housing-supply expansion inside the boundary and recommended pairing UGBs with policies such as minimum density requirements (rules obliging new development to exceed a floor of units per acre), zoning for multifamily housing, and accessory dwelling unit (ADU) ordinances (rules allowing small secondary units on single-family lots). The study itself could not verify this attribution: it did not observe the supporting policies' separate effects, had too short a price series to detect capitalization of boundary benefits as the market matured, and lacked any data on whether homebuyers value living inside versus outside the boundary.

The wider literature sharpens rather than answers the question. Studies of Oregon's UGBs have established that boundaries can contain development (Dempsey and Plantinga, 2013, a city-level difference-in-differences study of 17 Oregon cities that found significant negative effects of the boundaries on development in most of them) but do not decompose price effects. Within Oregon's regime, Lewis, Parker, Zou, Hovekamp, McGowen and Sherrard (2018) showed that a different sub-instrument of the same regime, voter-approved annexation (the incorporation of unincorporated land into a city, in Oregon subject to local voter approval), raises housing values and density with inequitable distributional effects - evidence that components of a growth-management package carry distinct price effects. Methodologically, Severen and Plantinga (2018) decomposed the price effect of the California Coastal Act (a land-use regulation applied along a jurisdictional boundary) into a local restriction effect (about 8 percent) and an external amenity effect (10-17 percent), demonstrating that such decompositions are feasible for boundary-style regulations - but no comparable decomposition exists for a UGB together with its supporting policies. The same author extended the King County analysis with two-stage quantile spatial regression (Mathur, 2019) - a method estimating the boundary's effect separately at different points of the house-price distribution rather than only on average - showing the UGB lowers house prices across the whole price spectrum but unevenly, which refines the magnitude question while leaving every channel question untouched. Two recent reviews - Siedentop, Schmidt and Dunlop (2022) on managing urban growth and Kirby, Scott, Luger and Walsh (2023) on the wider effects of urban growth management policies - both treat the economic effects of boundaries on land and housing markets as complex, location-specific, and incompletely understood, with Siedentop et al. explicitly noting that evaluating policies in isolation 'does not reflect the complexity of growth management programs.' A 2026 study of Riyadh's UGBs (Komo, Sho and Seta) concludes that rising land prices inside the boundary undermined affordability and that boundaries alone, without coordinated density and affordability policies, cannot deliver compact growth - restating, in a new context, exactly the interaction that remains unquantified.

Problem Statement

What determines the net housing-price effect of an urban growth boundary regime? Taking the King County, Washington urban growth boundary (UGB) - a regulatory line containing urban development - as the anchor case, where the boundary is estimated to raise land prices by roughly 230 percent while leaving house prices essentially unchanged or slightly lower, the problem is to decompose this net effect into its channels and establish which forces produce it. Specifically: (1) How much of the net housing-price effect is attributable to the boundary's restriction of land supply, how much to the capitalization of boundary benefits (cost savings, natural-resource preservation, overall economic efficiency) into house prices - that is, their gradual reflection in what buyers pay - as the housing market matures, a test requiring longer post-adoption time series than the original study window; and how much to the supply-expanding policies adopted alongside the boundary, namely minimum density requirements (mandatory floors on allowed development density), zoning for multifamily housing, and accessory dwelling unit ordinances (permissions for small secondary dwellings on single-family lots), whose individual and joint contributions have never been estimated? (2) Do homebuyers' preferences for living inside versus outside the boundary, unobserved in the original study, explain part of the observed price differentials? (3) Do the King County findings transfer to other metropolitan areas operating different growth-management frameworks and market conditions? These strands jointly serve one objective: to establish, with credible empirical identification, whether a UGB can avoid inflating housing costs and, if so, through which mechanisms - so that the boundary itself, its amenity benefits, and its supporting policies can each be judged as instruments of housing affordability policy rather than as an uninterpreted net number. The decomposition in question (1) addresses the core problem: a credible decomposition of the net housing-price effect into the boundary's land-supply restriction, the capitalized boundary benefits, and the individual and joint contributions of the supporting policies. Questions (2) and (3) extend it by examining the unobserved homebuyer-preference channel and the transferability of the King County findings.

References

  1. Mathur, Shishir (2014). Impact of Urban Growth Boundary on Housing and Land Prices: Evidence from King County, Washington. Housing Studies 29(1), 128-148. DOI: 10.1080/02673037.2013.825695. https://doi.org/10.1080/02673037.2013.825695
  2. Mathur, Shishir (2019). Impact of an urban growth boundary across the entire house price spectrum: The two-stage quantile spatial regression approach. Land Use Policy 80, 88-94. DOI: 10.1016/j.landusepol.2018.09.011. https://doi.org/10.1016/j.landusepol.2018.09.011
  3. Siedentop, Stefan; Schmidt, Stephan; Dunlop, Alistair (2022). Managing Urban Growth - an Overview of the Literature. Raumforschung und Raumordnung / Spatial Research and Planning 80(6), 659-677. DOI: 10.14512/rur.1653. https://doi.org/10.14512/rur.1653
  4. Kirby, Matthew G.; Scott, Alister J.; Luger, Jason; Walsh, Claire L. (2023). Beyond growth management: A review of the wider functions and effects of urban growth management policies. Landscape and Urban Planning 230, 104635. DOI: 10.1016/j.landurbplan.2022.104635. https://doi.org/10.1016/j.landurbplan.2022.104635
  5. Severen, Christopher; Plantinga, Andrew J. (2018). Land-use regulations, property values, and rents: Decomposing the effects of the California Coastal Act. Journal of Urban Economics 107, 65-78. DOI: 10.1016/j.jue.2018.07.001. https://doi.org/10.1016/j.jue.2018.07.001
  6. Lewis, Rebecca; Parker, Robert; Zou, Zhenpeng; Hovekamp, Winston; McGowen, Megan; Sherrard, Ryan (2018). Voter-Approved Annexations in an Urban Growth Boundary Regime: The Impacts on Housing Values, Density, and Economic Equity. Growth and Change 49(2), 286-313. DOI: 10.1111/grow.12235. https://doi.org/10.1111/grow.12235
  7. Dempsey, Judith A.; Plantinga, Andrew J. (2013). How well do urban growth boundaries contain development? Results for Oregon using a difference-in-difference estimator. Regional Science and Urban Economics 43(6), 996-1007. DOI: 10.1016/j.regsciurbeco.2013.10.002. https://doi.org/10.1016/j.regsciurbeco.2013.10.002
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  9. Komo, Wasem Mohammad A.; Sho, Kojiro; Seta, Fumihiko (2026). Effectiveness of Riyadh's Urban Growth Boundaries: An Evaluation Based on Building Permits, Vacancy, Road Infrastructure, and Land Price Variation. Japan Architectural Review 9(1), e70082. DOI: 10.1002/2475-8876.70082. https://doi.org/10.1002/2475-8876.70082