Portland is commissioning its own study on the “effects of inclusionary zoning,” as if the question was unsettled, novel, or open.
It isn’t.
Across the ideological spectrum, from UC Berkeley to NYU Law to George Mason and numerous think tanks, colleges, and studies across the country, the research record is remarkably consistent: inclusionary zoning reduces housing production and raises costs. This includes Maine Policy Institute’s own analysis, released this March, which analyzed the nationwide effects of inclusionary zoning and many other housing policies. Portland’s insistence on revisiting the issue is not evidence-based policymaking. It is an outright denial of economic reality.
Inclusionary zoning (IZ) requires developers to rent or sell a portion of new housing units at below-market rates, or to pay a fee instead. Whatever the moral appeal of these policies, in reality, they function economically like a tax on housing development.
This is not some partisan talking point; it is obvious, it is bipartisan, and it is a near-universal conclusion by those who have studied this policy.
The Research Consensus Portland is Ignoring
The Terner Center for Housing Innovation at UC Berkeley, working with UCLA’s Lewis Center for Regional Policy Studies, recently modeled the long-term effects of inclusionary zoning in Los Angeles. They found that after years of impact from the inclusionary zoning policy, IZ functions as a tax on development, reducing overall production and increasing prices.
Furthermore, it frequently eliminates multiple market-rate units for every subsidized housing unit created, reducing overall affordability and availability of housing. In some scenarios, the net loss exceeded twenty units per affordable unit produced. Notably, these findings come from institutions widely regarded as having strong left-leaning political reputations, underscoring that the critique of inclusionary zoning is empirical rather than ideological.
Seattle provides one of the cleanest real-world tests of this theory. A recent peer-reviewed paper examining Seattle’s Mandatory Housing Affordability (MHA) program, which ties upzoning to affordability mandates, used a difference-in-differences design to compare upzoned areas with and without the mandate. The result was unambiguous: new construction increased far less in areas subject to the affordability requirement, with construction substantially shifting away from those areas. Developers did not “build anyway.” They built elsewhere, or not at all.
NYU’s Furman Center, hardly a free-market outlier, has reached similar conclusions. Its research on Boston-area suburbs found that inclusionary zoning acts like a tax on development, correlating with reduced housing production and higher prices in surrounding markets. The National Center for Smart Growth Research and Education at the University of Maryland found that inclusionary zoning raised the price of single-family homes while simultaneously reducing their size and quality, a predictable response when policy forces developers to cross-subsidize units.
Even the U.S. Environmental Protection Agency, in guidance documents and case studies, acknowledges the fundamental economic reality: when affordable units are mandated, developers offset the cost by raising prices on non-restricted units or by not building at all if the mandate is set too high. This is especially true in slower or smaller markets like Portland’s, where projects simply become infeasible.
Across institutions, methods, and cities, the finding repeats itself: inclusionary zoning does not increase housing affordability at scale. It shrinks supply, increases prices, and benefits a narrow subset of households at the expense of everyone else.
So, Why is Portland Studying This Again?
Portland’s decision to commission its own study does not reflect prudence or wanting to “know all the facts”. It reflects a refusal to accept evidence until it agrees with their preconceived conclusions. Portland knows that it wants inclusionary zoning to work, even though the evidence shows it doesn’t, so it’ll keep asking the same question that has already been asked until it gets the answer it wants: “yes.”
Portland is not an exception to the rule. If anything, it is a worst-case scenario. The city already layers inclusionary zoning on top of rent control, restrictive zoning, energy mandates, and discretionary permitting. These policies do not operate in isolation; they compound. The result is visible in Portland’s own housing reports: large numbers of approved projects that are never completed, a growing backlog of expired permits, and a sharp decline in feasible multifamily development.
Commissioning another study does not change those incentives. It delays accountability while the housing shortage worsens.
Inclusionary Zoning Is Not a Housing Policy
In reality, inclusionary zoning is not a serious housing supply strategy. It is a redistribution policy disguised as construction. Cities adopt it because it appears to produce affordable units “for free,” without appropriations or hard budget choices. But the cost is real, and it is paid in fewer homes, higher rents, and stalled development. There’s no such thing as a free lunch, let alone a free apartment.
If Portland wants affordable housing, it should support it transparently and remove barriers to building. What it should not do is pretend that mandating private losses will somehow produce public abundance, especially when the evidence says the opposite.
The remarkable thing is that George Mason’s Mercatus Center, UC Berkeley, UCLA, NYU, UMD, and even EPA-adjacent research are all in unanimous agreement on this issue. When institutions with such different political leanings agree on housing policy and reach the exact same conclusion, policymakers should listen. But Portland has chosen not to.
