The United States is short millions of homes because, for decades, housing construction has not kept up with population growth. In response, many jurisdictions are hoping to expand housing supply through upzoning: reforming land-use rules to enable developers to build more housing units per parcel.

The theory behind upzoning is straightforward. If local regulations cap the number of homes a developer can build on a piece of land, raising those caps should result in more homes being built. More homes, in turn, should eventually translate to lower prices, as more supply can better accommodate demand. And this could provide people a broader range of neighborhood options and reduce displacement pressures. In practice, however, the chain from relaxed regulations to new homes is sometimes less automatic than the theory implies. Some detractors argue that upzoning does not produce new supply quickly enough meaningfully to improve housing affordability.

Even so, the growing body of evidence on upzoning suggests that this policy change can increase housing supply. But outcomes depend on local context, including market demand, reform design, and other housing policies.

Below, we summarize the latest research on the effects of upzoning and lift strategies policymakers can consider to ensure it effectively expands housing supply, notably through focusing on large-scale upzonings in hot-market neighborhoods.

How much additional housing does upzoning produce?

• Large-scale upzoning has been associated with meaningful growth in local housing supply. A 2025 study of New York City’s neighborhood rezonings found that the number of residential units on upzoned parcels grew by about 4 percent within seven years following reforms, with the parcels receiving the strongest boosts in allowed residential capacity experiencing as much as an 8 percent increase in housing units. A recent analysis by the Urban Institute of Philadelphia’s citywide zoning overhaul and neighborhood-level rezonings in New York City likewise fits this pattern: Growth in supply was substantially more likely in the upzoned areas compared with similar non-upzoned areas. We found that upzonings in New York were associated with 4,000 additional units, or roughly 0.17 new units per upzoned parcel, within four years after upzoning, compared with what we would otherwise expect.
• International evidence confirms that large-scale upzonings may produce substantial new housing. Studies of recent reforms outside the United States—including Auckland’s 2016 Unitary Plan, which upzoned about three-quarters of the city’s residential land; São Paulo’s 2016 block-level increases in allowed floor-area ratios; and a series of reforms in the Canton of Zurich—all identified substantial increases in permitting and construction on upzoned parcels. In Auckland, researchers estimated that upzoning produced on the order of 20,000 additional dwellings over 5 years, equivalent to roughly 5 percent of the region’s housing stock. In Zurich, upzoning a parcel by 20 percent or more led to a 13 percent increase in the number of housing units on that parcel over the following 10 years.
• When upzoning is relatively small or narrowly targeted, housing supply responses may be less effective. A Chicago reform that raised allowed densities by a relatively small degree alongside reduced parking requirements produced no significant increase in housing permits over the five years following passage, though property values on upzoned parcels rose, suggesting future interest in development. A study of San Jose, California’s 2011 “urban village” planning strategy, which designated a set of neighborhoods for higher-density, mixed-use development, similarly found that its effects on residential permitting, large development projects, and parcel transactions were generally indistinguishable from zero, with the authors attributing the null result to a combination of regulatory and market factors. A limited set of reforms in Portland, Oregon, had modest effects on redevelopment: Only 5.1 percent of upzoned parcels were developed after land-use changes because most lots were already built on, and the upzoning wasn’t large enough to compensate for the costs of redevelopment. Similarly, Minneapolis's rezoning of single-family-only districts to allow duplexes and triplexes has not yet led to an uptick in overall residential permitting, though this reform is part of a broader upzoning package and some formerly single-family parcels have seen larger multifamily development where those provisions apply.
• When upzoning is coupled with costly mandates, the supply response may be muted. In Seattle, parcels subject to the city’s Mandatory Housing Affordability program experienced lower new-construction permitting relative to those parcels just outside the border; developers appear to have strategically sited projects just outside of the upzoned boundaries to avoid the program’s affordable housing requirements. And a recent national analysis using the National Longitudinal Land Use Survey finds that municipal-level upzoning alone, measured in this case as a change in maximum allowable density, is only inconsistently associated with increases in actual density. These results suggest that outcomes at the parcel and neighborhood levels depends heavily on local conditions and on what else is changing in the regulatory environment.

How quickly does upzoning produce housing?

• When upzoning involves multifamily development, the supply response may take several years. A 15-year study of upzoned parcels in Portland, Oregon, finds that the average project took nearly 8 years to complete after upzoning. In our analysis of Philadelphia’s zoning overhaul, the bulk of the supply response to the 2012 reform did not manifest until several years after passage, once a separate tax abatement program had begun to reshape developer economics and the city council made additional changes to the city’s zoning map.
• When upzoning targets accessory dwelling units (ADUs), responses may be much faster. Los Angeles went from 93 ADU completions in 2016 to more than 3,100 in 2020 after a combination of reforms at the state and city levels that made it more feasible to build ADUs. Portland was far more effective in encouraging ADU investment than was Washington, DC, because its reforms were associated with fewer requirements, such as mandating homeownership of at least one of the units on-site.
• The effect of upzoning on housing supply may grow over time. A study of New York City’s upzonings from 2002 to 2013 (PDF) similarly finds that effects in the first few postreform years are small but grow 6 to 12 years after upzoning. This suggests caution when interpreting early evaluations of recent reforms—especially when outcomes are delayed by litigation and other challenges, as was the case in Minneapolis. A 20-year examination of upzoned sites across 19 activity centers in Brisbane, Australia, finds that roughly 78 percent of sites with added zoned capacity in the first period remained undeveloped two decades on, with only about 2 percent of zoned capacity taken up in any 5-year window.

Where does upzoning lead to new construction?

• When upzoning happens, construction tends to concentrate on parcels suited for redevelopment. The Portland analysis finds that parcels developed after upzonings were constructed at nearly 65 percent higher densities than comparable, non-upzoned parcels. The author concludes that upzoning is most effective when applied to vacant and underutilized parcels. Similarly, the Chicago upzoning’s effects on property values were largest for vacant land, and the Minneapolis upzoning’s effects on values were largest for small, older homes, suggesting that the upzoning may ultimately result in more building on those underutilized properties.
• When upzoning occurs in weak-market neighborhoods, little new housing may follow. A study of New York City’s neighborhood-level rezonings found heterogeneous effects: Housing stock growth was concentrated in higher-demand neighborhoods, while upzoned low-income neighborhoods saw signs of gentrification and higher housing costs without meaningful increases in supply. Our own analysis of New York City’s neighborhood rezonings pointed in a similar direction: The Jerome Avenue corridor in the Bronx—which had the slowest pre-upzoning rent growth of any of the upzoned neighborhoods studied—showed no statistically significant change in housing supply. On the other hand, the Gowanus neighborhood, which was adjacent to areas with growing, high rents (suggesting high demand), experienced a quick and large increase in housing development after upzoning.

Upzoning’s effects on affordability and neighborhood demographics

• Additional housing moderates housing costs, but not always for the lowest-income households. A review of the housing-supply literature finds that new homes improve housing availability for low- and moderate-income families, though additional supply alone is insufficient to produce affordability for the lowest-income households. A research roundup on the effects of market-rate development on neighborhood rents similarly finds that new market-rate development moderates nearby rents, though the magnitude varies, and a small number of studies find localized price increases in areas already undergoing gentrification.
• When neighborhoods are upzoned, early evidence points to associated demographic shifts. A study of New York City’s 2002 to 2009 rezonings finds that upzoning activity was positively and significantly associated with the odds of a census tract more populated by white people, with another recent analysis finding that these gentrification trends were strongest in intensely upzoned, high-demand areas. A recent study of Los Angeles and San Francisco suggests that increased housing supply could exacerbate the out-migration of households with low and moderate incomes, at least unless they are supported through access to subsidized, affordable housing options. Another New York City analysis finds that incumbent residents in upzoned neighborhoods were somewhat more likely to move, but not disproportionately toward lower-income areas.

Lessons learned: How to achieve more effective upzoning

A growing body of evidence, including our own analyses of New York City and Philadelphia, suggests upzoning can contribute to new housing supply when the right conditions are in place. But more research is needed before firm conclusions can be drawn about upzoning’s impacts, particularly at the regional scale and over longer time horizons.

Moreover, upzoning is just one of several interrelated strategies needed to improve housing affordability and availability, especially because its effects take time to emerge. Subsidized housing designed to be affordable for households with low and moderate incomes, for example, is often dependent on higher-density zoning, because such units tend to be built in multifamily buildings.

When policymakers are weighing whether and how to upzone, a few considerations can inform whether the policy is likely to produce new housing:

• Larger increases in zoned capacity will likely produce larger increases in housing supply. Policymakers should weigh whether the proposed reform is large enough to meaningfully shift what can be built on a particular site. If existing zoning is not a binding constraint on development (meaning housing isn’t being built in that area for reasons other than zoning), upzoning is unlikely to generate new housing. Where existing zoning is binding, the upzoning must be large enough to justify the often-costly demolition of existing uses and the new construction of bigger buildings on the same site. In addition, raising allowed densities alone often isn’t enough to make projects feasible; parking minimums, lot-size rules, and setback requirements can remain binding constraints even after an upzoning. Policymakers should consider the full package of land-use rules alongside the density change to ensure the rezoning will make projects possible.
• Upzoning in areas with strong housing markets is likely to be more effective. In weaker-market neighborhoods—those with lower rents and housing values—upzoning alone is unlikely to produce much new housing. That’s because developers must be confident that there will be adequate demand from new residents to provide a return on their investments. In stronger-market neighborhoods, requirements that add to the cost of building, such as affordability requirements attached to additional allowed units, can reduce how much new housing gets built, while policies that lower costs, such as permitting reforms to shorten approval times, can strengthen the supply response.
• Housing development takes years to complete. Because supply responses to upzoning typically take years to materialize, policymakers should set expectations accordingly and be cautious about drawing conclusions from early evaluations. In particular, they should monitor demographic changes in affected communities and pair upzoning with targeted interventions, such as investments in affordable housing to prevent displacement of households with low and moderate incomes and to ensure upzoned neighborhoods offer a diversity of homes for families with a variety of incomes.