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Housing costs in major American metropolitan areas have risen dramatically faster than incomes for decades, and the affordability gap has widened substantially since 2015. The consequences are visible: displacement of long-term residents, extreme commutes as workers seek affordable housing far from job centers, homelessness, and intergenerational wealth concentration among homeowners while renters fall further behind. The causes are multiple, including construction costs, interest rates, land prices, and investor demand. But a significant contributor is housing supply restriction through zoning, and zoning is a policy variable that local governments have the authority to change.

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== How Zoning Restricts Supply ==

Most American cities zone the majority of their residential land exclusively for single-family detached housing, prohibiting the apartment buildings, townhouses, and mixed-use development that would add housing supply and reduce per-unit cost. In the San Francisco Bay Area, over 90 percent of residential land is zoned for single-family use only. In Los Angeles, the proportion is similarly high. These restrictions are not natural features of urban geography. They are regulatory choices, made by local governments over decades, often with the explicit or implicit goal of maintaining property values for existing homeowners by restricting the supply that would otherwise compete with existing housing stock.

The consequences of supply restriction are mathematically predictable and empirically confirmed. When demand for housing in a location grows, as it does in economically productive cities that attract workers, and supply cannot grow to match, prices rise. The households with the lowest incomes are displaced first. The households that remain pay more. The workers who cannot afford to live near their jobs commute from far away, adding congestion, pollution, and personal cost. The employers whose workers cannot afford to live nearby face recruitment and retention challenges that constrain growth. The fiscal costs of homelessness, displacement, and inadequate housing ripple through public budgets.

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== What Reform Looks Like ==

A growing number of cities and states have adopted zoning reforms that meaningfully expand housing supply potential. Minneapolis eliminated single-family-only zoning citywide in 2040, allowing duplexes and triplexes in all residential zones. Oregon eliminated single-family-only zoning for cities above 10,000 residents statewide. California eliminated single-family-only zoning statewide and streamlined permitting for accessory dwelling units, producing a dramatic increase in ADU construction. Eliminating parking minimums, which add $20,000 to $50,000 per space to construction costs, reduces per-unit costs and allows more housing on a given parcel.

The evidence on the housing supply and affordability effects of these reforms is beginning to accumulate. Minneapolis has seen faster housing production growth and slower rent increases than comparable peer cities since its 2040 plan was adopted. California's ADU streamlining produced a 10-fold increase in ADU permitting within three years of enactment. Research on the price effects of new market-rate housing construction consistently finds that new supply reduces rents in nearby areas over time, including at the lower end of the market, because new housing relieves pressure on the existing stock. The effects take time to materialize and are larger in already tight markets.

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== Political Economy of Reform ==

Zoning reform is politically difficult because the people who benefit most from housing supply growth, renters and future residents, are diffuse and often not present in local planning processes, while the people who may bear costs from nearby development, existing homeowners, are organized and engaged. Sustained reform requires building political coalitions that make the case for housing supply as a public good, not just a private market outcome, and that connect zoning reform to broader goals of economic opportunity, environmental sustainability through transit-oriented density, and racial equity in housing access that was historically constrained by exclusionary zoning that was explicitly racial in its origins.

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''Originally published April 3, 2020 on [https://docmoates.com/blog/zoning-reform-and-housing-affordability-the-policy-levers-that-matter/ docmoates.com].''