Planopedia

The term YIMBY, which stands for "Yes In MY Backyard," describes a pro-development political stance that generally supports planning and building at larger scales than the country's history of sprawl, single-family zoning, and car-centric planning has allowed. The primary idea behind the YIMBY movement is that land use regulations, such as zoning codes, should be reformed to allow more housing to be built. By building more housing, the YIMBY argument goes, the market will provide more housing options at various income levels and will limit the environmental impacts of unfettered sprawl.

The YIMBY acronym was invented to respond directly to the older term, NIMBY, for "Not in My Backyard." By comparison, NIMBY is generally pejorative—you won't often hear anti-development forces using the term NIMBY to describe themselves. YIMBYs, both individuals and organizations, do use the term YIMBY to describe themselves, and are very clear about their goal of advocating and legislating for reforms that make it easier to build housing as a tool for improved affordability.

The organization YIMBY Action, for example, describes itself as "a network of pro-housing activists fighting for more inclusive housing policies and a future of abundant housing," adding, We drive policy change to increase the supply of housing at all levels and bring down the cost of living in opportunity-rich cities and towns."

Considered in context of each other, the terms NIMBY and YIMBY contest some of the most fundamental debates of planning: what to build, where, and how much. YIMBYs and NIMBYs contest this ground in court and in the legislature, in a constant push and pull of regulation and litigation with results that vary by local and state jurisdiction. Despite the well entrenched political power of anti-development forces, YIMBYs have ascended into the political mainstream, with a string of substantive political, legislative, and legal victories (more on the rise of the YIMBY). YIMBYs can claim recent political victories in California, Oregon, and Minneapolis, with laws that have ended the use of single-family zoning to ban all forms of residential development other than single-family detached homes. YIMBYs have also pushed for reforms of parking requirements, resulting in a string of ordinances removing or lowering parking requirements in cities like Boston, San Diego, and Toronto. 

Still, YIMBYs have a long way to go in achieving a full realization of their vision even in the cities and states most committed to implementing the YIMBY policy agenda. In the ongoing debate, each side presents the other as inherently misguided or deliberately misleading. NIMBYs claim that YIMBYs serve the interests of wealthy developers and landlords. YIMBYs argue that NIMBYs are protecting their self-interest above the public good, often by disguising discriminatory intentions behind cleverly-phrased euphemisms. 

Market-Rate Housing and the Key Question of Filtering

An informed opinion on YIMBY politics requires consideration of the effects of market-rate housing development on the larger housing market (market-rate housing is built without public subsidy or other mechanisms, such as inclusionary zoning, to spur the creation of housing affordable at lower income levels). Despite their success in recent years in loosening zoning restrictions in a few cities and states, YIMBYs have yet to build a coalition that includes anti-gentrification advocates, due to unresolved questions about the effect of market-rate housing development on gentrification and displacement in neighborhoods with large shares of low-income and BIPOC residents.

While YIMBY activists claim that their desired pro-development reforms are designed to respond to the discriminatory effects of exclusionary zoning by increasing the total number of housing units on the market, lessening the competition for any given housing unit at any given price point. Many anti-gentrification advocates are skeptical, however, that market-rate housing accomplishes anything other than raising rents and property taxes throughout the neighborhood, thus pricing out the existing community. 

At the heart of this debate about the effect of market-rate housing developments is a dynamic known as filtering, i.e., a process by which market-rate housing units age and decline in value, becoming affordable to a wider segment of the market—becoming what is referred to as "naturally occurring affordable housing" while newer market-rate housing units replace the supply of more expensive housing units. YIMBYs make the argument that without a steady supply of new market-rate units, wealthier residents are forced to compete for older units with lower-income residents—a classic imbalance between supply and demand that increases prices throughout the market and leaves many potential residents looking for solutions at lower ends of the market or, failing that, in more affordable locations. 

Both sides, YIMBYs on one side and anti-gentrification advocates and supply-side skeptics on the other, can point to evidence to support their cause. 

On the side of skepticism, housing demand has been shown to be relatively inelastic—meaning increasing housing supply doesn't always produce the expected result of lower housing prices. Similar to the way induced demand works for transportation demand, new housing supply activates latent demand in the market, quickly overwhelming the new capacity. Researchers have found that the elasticity of demand differs by geographic region—with high-demand cities more inelastic that other cities. European researchers have found evidence that the U.S. housing market has become less elastic in recent decades.

Yonah Freemark, a senior research associate at the Urban Institute, published research in 2019 finding evidence that upzoning, a favorite cause of YIMBYs but a favorite target of opposition from NIMBYs and anti-gentrification advocates, failed to deliver new housing supply and resulted in increased housing prices when applied for transit oriented development in Chicago.

Researchers have also produced a stream of findings that support YIMBY arguments in recent years, however. Planetizen blogger Todd Litman, for example, has documented studies supporting the idea that filtering produces naturally occurring affordable housing. A 2020 new paper by researchers at the Federal Home Loan Mortgage Corporation (Freddie Mac) also found evidence of filtering working as YIMBYs intend. Most recently, a study from Finnish researchers in September 2021 found that 100 new, centrally located market-rate units will create vacancies for roughly 60 units in the bottom half of neighborhood income distribution.

In a direct contradiction of Freemark's study and the common arguments against YIMBY policies, a May 2021 study published in The Review of Economics and Statistics found evidence that adding new housing in low-income neighborhoods supply lower prices in the surrounding neighborhood.

Other IMBY-isms of Note

The popularity of the terms NIMBY and YIMBY in planning discourse has seen the rise of other terms that also rely on the "In My Backyard" formula for acronyms, including PHIMBY (i.e., "Public Housing In My Backyard") and QUIMBY (i.e., "Quality In My Backyard").