The Inclusionary Zoning Paradox: How "Affordable Housing" Mandates Make Housing Less Affordable

The United States faces a housing shortage of 3.7 million units, according to Freddie Mac's most recent estimate. Against that backdrop, more than 800 American cities have adopted "inclusionary zoning" — ordinances that require private developers to set aside a percentage of new housing units at below-market prices as a condition of building at all. The policy's appeal is intuitive: make developers create affordable housing, at no direct cost to taxpayers, and the problem solves itself. The reality, documented by researchers across the ideological spectrum, is that inclusionary zoning reliably reduces overall housing supply, raises market-rate prices, and produces an embarrassingly small number of affordable units in return. It is, in the language of economics, a tax on new construction, and like all taxes on production, it produces less of what we need most.

What Inclusionary Zoning Actually Is

Inclusionary zoning (IZ) policies were first implemented in Fairfax County, Virginia, in 1971. They now exist in more than 800 jurisdictions across the United States. Requirements vary: some mandate that 10% to 20% of units in new developments be rented or sold at below-market rates. Others are nominally voluntary, offering density bonuses — permission to build slightly more — in exchange for dedicating units to income-qualified households. In practice, where base zoning is already restrictive, "voluntary" programs are coercive in all but name. New York City's Mandatory Inclusionary Housing (MIH) program, launched in 2016, requires affordable set-asides for nearly all large residential developments that seek a zoning change — a requirement that, given how restrictive the baseline zoning is, applies to virtually every significant project in the city.

The mechanism of IZ looks superficially like a subsidy, but it is actually a mandate that forces one private party (the developer) to subsidize another (the below-market-rate tenant) as a precondition for engaging in an otherwise legal activity. Milton Friedman, who spent his career cataloguing the unintended consequences of exactly this kind of regulatory structure, would have recognized IZ immediately: a well-intentioned intervention that distorts price signals, discourages production, and ultimately leaves the intended beneficiaries worse off than a liberalized market would.

The Supply Effect: IZ as a Tax on Construction

Basic price theory predicts what happens when you impose an additional cost on producers: output falls and the cost is passed through to remaining consumers. IZ does precisely this. A developer who must rent 15% of a building's units at half the market rate must recover that lost revenue somewhere — either by raising prices on the market-rate units, by building a smaller project, or by not building at all.

The empirical evidence confirms the theory. A 2024 study from the UCLA Lewis Center for Regional Policy Studies, published by the Terner Center at UC Berkeley, modeled the effects of varying IZ requirements on housing production in Los Angeles. The findings were stark: completely eliminating IZ requirements in transit-eligible zones — while maintaining existing density bonuses — would yield approximately 398,800 homes over ten years. That is 38% more than would be built under the current 11% IZ requirement. Every additional percentage point of IZ requirement, the study found, reduces market-rate production by between 4,600 and 11,900 units. At a 17% IZ requirement, market-rate production is cut in half. At 20%, a mandate that would produce 50,000 below-market units would simultaneously eliminate more than 200,000 market-rate homes.

The California experience during the 1990s offers a natural experiment. A study cited by the Manhattan Institute found that California municipalities that adopted inclusionary zoning in that decade saw house prices rise 20% higher and total housing stock fall 7% below what comparable municipalities without IZ achieved over the same period — a period when demand was expanding rapidly. The cities that mandated affordability produced less housing and higher prices than those that did not.

In Portland, Oregon, the effect was visible in the project-size data: after the city's IZ ordinance applied to buildings of 20 units or more, new apartment projects just above the 20-unit threshold essentially disappeared, while projects of 19 units proliferated. This is a textbook response to a threshold tax — developers optimize around the trigger rather than build what the market needs.

The Output Problem: 27 Units Per Year

Even setting aside the supply-destruction effects, IZ programs produce remarkably little affordable housing in absolute terms. According to an analysis of IZ programs across the country, the average IZ program produces only 27 units of affordable housing per year. Across 800 programs, that amounts to roughly 21,600 units annually — a number that barely registers against a national housing deficit of 3.7 million and a household formation rate that outpaces total construction by hundreds of thousands per year.

San Francisco, one of the most aggressive IZ jurisdictions in the country, has accumulated approximately 5,000 inclusionary housing units over the life of its program — in a city where median home values exceed $1.2 million and housing unaffordability is among the most acute in the nation. Five thousand units, in a city of 870,000 people, over multiple decades, delivered at the cost of suppressing tens of thousands of additional market-rate units that would otherwise have been built. This is not a housing policy success. It is a monument to the difference between good intentions and effective outcomes.

The Price Pass-Through: Market-Rate Units Pay the Bill

IZ doesn't eliminate the cost of below-market units — it merely shifts who pays for them. Those costs are absorbed by market-rate buyers and renters in the same development. NAHB research confirms that IZ requirements function as an additional tax on developers, who respond by constructing smaller buildings, charging higher prices on unrestricted units, or relocating projects to jurisdictions without mandates.

The Terner Center modeling found that even small increases in market rent — as little as 0.8% per year in additional rent growth — would be enough to completely negate the private subsidy value that IZ programs generate for low-income tenants. In other words, the inflation in market rents caused by reduced supply can erase the financial benefit to the very households IZ is designed to help. The policy robs Peter to pay Paul, but in the process drops enough money in transit that Paul ends up worse off.

Thomas Sowell's "Basic Economics" opens with the observation that economics is the study of the use of scarce resources which have alternative uses. Inclusionary zoning violates this principle at every turn: it treats developer capacity as a free resource to be commandeered, ignores the alternative uses of that capital (which include building more unrestricted units elsewhere or not at all), and assumes price controls on a subset of units will not affect behavior in the broader market. Every economic prediction that flows from this analysis has been borne out in the data.

The Perverse Incentive Structure

IZ creates a second-order problem that Hayek would have categorized as a knowledge problem: it gives affordable housing advocates a political reason to support policies that keep market-rate housing artificially scarce. If IZ benefits depend on base zoning remaining restrictive — because "voluntary" density bonuses are only valuable when base zoning denies that density — then the coalition that benefits from IZ has an institutional interest in keeping restrictive zoning in place. Advocates for IZ and advocates for exclusionary zoning end up, paradoxically, defending the same regulatory structure.

This helps explain why IZ has persisted and spread despite weak evidence of effectiveness. It provides visible, tangible benefits to a small number of below-market tenants (and politically valuable photo opportunities at ribbon-cuttings) while distributing its costs diffusely across all market-rate renters and would-be homebuyers — exactly the dynamic that public choice theory predicts will sustain bad policies indefinitely.

What Works Instead

The Terner Center study is explicit about the policy implication: "policymakers should focus on land use reforms to increase overall housing production" rather than relying on IZ mandates. This is the supply-side prescription that flows naturally from price theory and is confirmed by the empirical record. The elimination of exclusionary single-family zoning — which prohibits multifamily housing on roughly 75% of residential land in most American cities — would expand the supply of units across all price points far more effectively than IZ ever could. Cutting the regulatory compliance costs that add nearly $94,000 to every new home built would make construction financially viable in more markets, without requiring developers to cross-subsidize below-market units.

Where affordable housing subsidies are genuinely needed, directing them through the public budget — rather than commandeering private developer capacity — is both more transparent and more effective. A subsidy funded by general tax revenue distributes the cost broadly and allows policymakers to weigh it directly against alternatives. IZ hides that cost inside a regulatory mandate, where it is diffuse, invisible, and politically costless to impose — which is precisely why politicians favor it over more honest approaches.

The Policy Lesson

Inclusionary zoning is not a failure of implementation. It is a failure of economic logic. A policy that imposes a production tax on the one activity (market-rate construction) capable of expanding overall housing supply cannot, by design, produce more housing. It can only redistribute a shrinking pie while claiming credit for baking it.

The 800 cities that have adopted IZ have each run a version of the same experiment, and the results are consistent: fewer total units built, higher prices for market-rate renters, and a trickle of below-market units that vanishes against the scale of actual need. Against a national shortage of 3.7 million homes, producing 27 units per program per year is not a housing policy. It is the appearance of one.

The path to genuinely affordable housing runs through supply — liberalized zoning, reduced regulatory burden, and the freedom to build where demand exists. Policies that tax construction in the name of affordability are not reforms. They are the problem wearing a different name.

The Inclusionary Zoning Trap: How "Affordable Housing" Mandates Destroy the Supply They Promise to Create

Folded in from a companion piece first published March 19, 2026. Its figures and sources are preserved below.

There is no better illustration of the law of unintended consequences in housing policy than inclusionary zoning. Across more than 800 American cities, local governments require developers to sell or rent a fixed percentage of new units at below-market prices — a mandate that sounds like an obvious solution to the affordability crisis. The logic is seductive: developers build housing anyway, so why not extract a quota of affordable units from each project? The problem, as a growing body of empirical evidence confirms, is that this logic inverts basic price theory, and the results are housing markets with less of everything: fewer market-rate homes, fewer below-market homes, and higher prices for everyone.

The Economics of a Subsidy Mandate

Inclusionary zoning (IZ) is, at its core, a tax on new residential construction. When a municipality requires that 15 or 20 percent of units in a new building be priced at, say, 60 percent of area median income, it is compelling developers to sell those units at a loss, and mandating that the remaining market-rate buyers absorb the subsidy. Developers are not charities. The cost of each below-market unit gets redistributed across the rest of the project, raising prices for market-rate buyers and shrinking the pool of financially viable projects.

This is not a controversial observation. It is standard microeconomics. A price ceiling on a portion of a good, financed by a price floor on the remainder, reduces total quantity supplied. Milton Friedman observed that price controls, wherever applied, reliably produce shortages. Inclusionary zoning applies exactly this logic to housing — with precisely the predicted result. The Mercatus Center at George Mason University documented that despite more than five decades of IZ programs nationwide, the total number of affordable units produced since inception is estimated at only 129,000 to 150,000 — a national drop in the bucket against a shortage measured in the millions of units.

The UCLA Terner Center's Stark Trade-Off

The most rigorous recent analysis of this trade-off comes from a 2024 study by the UCLA Lewis Center for Regional Policy Studies, published by the Terner Center for Housing Innovation at UC Berkeley. Focusing on Los Angeles's Transit Oriented Communities program, the study modeled what happens to total housing production as IZ requirements increase. The findings are striking.

Each percentage-point increase in IZ requirements between 1 and 16 percent is associated with the elimination of between 4,600 and 11,900 market-rate units. At a 20 percent IZ requirement, the model predicts that while 50,000 below-market units would be created, over 200,000 market-rate units would be destroyed. That is a net loss of 150,000 homes — a four-to-one destruction ratio. The study was explicit: beyond a certain threshold, higher IZ requirements produce less affordable housing and less market-rate housing simultaneously. The policy devours itself.

Portland and San Francisco: Case Studies in Policy Failure

Abstract modeling becomes concrete reality in two of America's most expensive cities. Portland, Oregon adopted a mandatory inclusionary housing fee in 2017. The result was immediate and severe: housing permits in the city fell from 5,094 units in 2019 to 1,779 units in 2020 — a collapse of 65 percent. Developers did not simply absorb the mandate; they moved their capital to surrounding suburban jurisdictions just outside Portland's limits. As the Sightline Institute documented, multifamily permit filings within Portland fell 40 percent from their 2016 peak, while the Tigard Triangle and Vancouver waterfront saw a surge of new construction. The IZ mandate had effectively exported Portland's housing supply to its suburbs, reducing total affordability within the city while doing nothing to address regional demand.

San Francisco offers an even more instructive case. For decades, the city maintained one of the most aggressive inclusionary mandates in the country — roughly 22 percent of units in new on-site developments required to be affordable. Then, in 2023, San Francisco's own Technical Advisory Committee found that no residential project prototype it studied would be financially feasible under those requirements. Development had ground to a near-halt. In response, the city that pioneered aggressive IZ quietly reduced its requirement to approximately 12 percent — an implicit admission that its mandate had been strangling the very supply it sought to supplement.

The Arithmetic of 27 Units Per Year

Step back from the case studies and examine the aggregate national performance. According to data compiled by Inclusionary Housing, the average production rate across all IZ programs in the United States is 27 affordable units per year per program. The top 20 programs average 235 units annually, but those are outliers in a landscape of hundreds of programs producing almost nothing. Meanwhile, the National Association of Home Builders estimates that 74.9 percent of U.S. households — roughly 100.6 million families — cannot afford the median-priced new home of $459,826 in 2025. The mismatch between IZ output and housing need is not a gap; it is a chasm.

Thomas Sowell's insight applies directly here: "There are no solutions — only trade-offs." Inclusionary zoning mandates represent a particularly costly trade-off: trading a small number of subsidized units in exchange for a much larger reduction in total housing supply, with the additional side effect of raising prices for every market-rate buyer in the city. It is a policy that takes from the many to give to the few, while ultimately failing even the few.

The Density Bonus Illusion

Proponents of IZ frequently point to density bonuses — allowances to build more total units than base zoning would permit — as the mechanism that makes IZ financially viable. The argument is that a developer required to set aside 15 percent of units at below-market rates can offset that cost by building a taller or denser building. This is theoretically sound as far as it goes. But as the National Association of Home Builders has noted, the density bonuses embedded in IZ programs derive their value entirely from the underlying exclusionary zoning that restricts development in the first place. The density bonus does not create value; it partially returns value that exclusionary zoning has already destroyed. A city that simply reformed its base zoning to allow higher density would achieve the same (or greater) housing production at zero cost to affordability — without the mandatory subsidy extraction.

Friedrich Hayek's concept of the knowledge problem is instructive here. City planners setting IZ percentages do not have access to the project-level financial models, land acquisition costs, construction debt terms, or local market conditions that determine whether a given development pencils out. They set a single mandatory rate and apply it uniformly — blind to the enormous variation in project feasibility. The result, predictably, is that the mandate is set either too low to produce meaningful affordable units, or high enough to kill development entirely. There is no centrally optimal rate, because the information required to calculate it is dispersed, local, and constantly changing.

What Actually Works

The evidence on IZ is not uniformly negative — programs with modest mandates, well-calibrated density bonuses, and strong underlying market demand do produce affordable units without catastrophically suppressing total supply. But these programs are the exception, not the rule. And in every case, the affordable units produced represent a fraction of what unrestricted market construction could deliver through the filtering mechanism — as older market-rate housing depreciates into the affordable stock over time.

The most effective interventions to improve housing affordability share a common feature: they expand supply rather than restrict it. Eliminating single-family zoning exclusions, streamlining permitting timelines, reducing impact fees, and allowing density by right all increase total housing production without extracting subsidies from new buyers. When governments stop taxing the construction of housing and start enabling it, housing gets built, and affordability follows. Inclusionary zoning, however politically appealing, achieves the opposite: it taxes supply in the name of subsidizing demand, and ends by delivering less of both.