Urban Wire Jurisdictions Dominated by Single-Family Zoning Hoard Opportunities, but Bans Aren’t the Only Fix
Lydia Lo
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Puget Sound neighborhood
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The traditional image of the American dream features a white picket fence surrounding a charming single-family home, nestled in a quiet suburban neighborhood. This ideal has shaped the development patterns of countless cities and towns, with single-family zoning becoming the norm across the United States.

Recent debates surrounding urbanization, housing affordability, racial segregation, and socioeconomic disparities, however, have prompted an interrogation of this long-standing practice. States such as California, Oregon, and Washington have gone so far as to pass legislation banning single-family-only zoning across most of their cities. But are single-family zoning bans necessary? Although much of this debate focuses on housing affordability, we don’t have enough evidence about how single-family zoning affects racial equity and upward social mobility within and across jurisdictions to say definitively that bans are effective.

To inform this ongoing policy conversation, I explored the relationship between zoning, racial equity, and social mobility by comparing zoning atlas data on number-of-unit zoning—defined as the maximum number of units allowed on an individual parcel—with census data and social capital data in Connecticut and the Puget Sound region. I find that zoning’s relationship with neighborhood demographics and potential for boosting upward social mobility is largely influenced by two factors: whether a neighborhood is exclusively zoned for single-family home construction and whether the jurisdiction as a whole has a large share of land zoned only for single-family homes. These findings indicate states don’t have to ban single-family zoning entirely to advance equity and upward social mobility.

Type of zoning and the shares of zoning types in an area can influence equity and social mobility

My team’s research documents how types of zoning correlate closely with race, income, and housing tenure patterns. Multifamily-zoned neighborhoods tend to be renter-occupied, more racially diverse, and lower income, while single-family zoned neighborhoods tend to be owner-occupied, white, and higher income. As such, the type of zoning is an indirect mechanism for income segregation.

In the Puget Sound region, only 24 percent of homes in neighborhoods zoned for multifamily housing are owner-occupied—in contrast to 74 percent of homes in neighborhoods zoned for single family housing. Although Washington state law will eliminate this distinction between jurisdictions by banning most single-family-only zoning in the coming years, the comparison still offers a portrait of a common discrepancy in other states.

This segregation becomes even more extreme between jurisdictions, and it happens when larger shares of jurisdictions are zoned for single-family housing. Jurisdictions with more than 75 percent of their land dedicated to single-family zoning (what I call high-SFZ jurisdictions) overall tend to be wealthier and whiter and have higher incomes, higher homeownership rates, and higher potential for boosting upward social mobility than jurisdictions with less than 75 percent of their land dedicated to single-family zoning (low-SFZ jurisdictions).

Looking at housing tenure, for example, tracts zoned almost entirely for multifamily housing (four or more housing units allowed per parcel) in low-SFZ jurisdictions in the Puget Sound had 27 percent owner-occupied housing, while similar tracts in high-SFZ jurisdictions had 53 percent owner-occupied housing. And in tracts largely zoned for single-family housing, low-SFZ jurisdictions had 69 percent owner-occupied housing while largely single-family zoned tracts in high-SFZ jurisdictions had 80 percent owner-occupied housing. Connecticut zoning and tenure follows the same trend lines.

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Additional analysis shows that high-SFZ jurisdictions in Connecticut and the Puget Sound region have residents with significantly higher incomes, have higher concentrations of white and high-income residents (i.e., higher Index of Concentration at the Extremes scores), and—in the case of the Puget Sound—are even closer to jobs and economic opportunities compared with low-SFZ jurisdictions. Low-SFZ jurisdictions also tend to have lower costs of living and higher variation in incomes, home values, and residents of color across their zones than high-SFZ jurisdictions (see table below).

In essence, high-SFZ jurisdictions hoard opportunities (e.g., access to well-resourced schools, grocery stores, unpolluted environments) by producing less housing than would be expected given their proximity to job centers, such that even their multifamily units are only accessible to higher-income homeowners. These findings are similar within Connecticut and the Puget Sound. They indicate that residents’ upward social mobility could be improved nationally by increasing access for renters with low incomes to neighborhoods and jurisdictions dominated by single-family housing.

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Source: Author analysis of Puget Sound Zoning Atlas and Connecticut Zoning Atlas data and 2015–19 American Community Survey (ACS) data.
Notes: ICE = Index of Concentration at the Extremes; SFZ = single-family zoning. High-SFZ jurisdictions were those where more than 75 percent of land was dedicated to single-family zoning, and low-SFZ jurisdictions were those with less than 75 percent of land dedicated to single-family zoning. Puget Sound data were divided by majority single-family tracts (i.e., tracts with greater than 75 percent of land dedicated to single-family zoning) and multifamily tracts with greater than 75 percent of land dedicated to 4+ unit zoning. Connecticut’s zoning data had ACS data characteristics interpolated by area and aggregated at the zoning district level, and thus used the direct ACS characteristics of zoning districts.

a ICE Income is calculated with the equation: (Ai – Pi)/ Ti , where Ai is the number of people in the top regional income quintile living in tract i, Pi is the number of people of in the bottom regional income quintile in tract i, and Ti is the total population of the tract i. Negative values indicate by how many percentage points people with low incomes surpass the share of those with high incomes. Positive values indicate the reverse. ICE race was constructed with the same formula but compared white, non-Hispanic residents (+) with all other racial and ethnic group residents (–). ICE tenure was constructed comparing owner-occupied housing units (+) compared with renter-occupied units (–). Economic connectedness scores measure the potential for children from households with low incomes to rise to a higher economic class (PDF). These scores were published at the zip code level and areally interpolated to the tract and zoning district level. Standard errors for these granular geographies are high, and these scores are suggestive at best; more granular research is needed to test the relationship between zone type and socioeconomic mobility.

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Policymakers can advance equity by encouraging residential income integration

These trends have implications for the regions’ potential to promote upward social mobility. High-SFZ jurisdictions have higher economic connectedness scores (an indicator based on Raj Chetty’s research that measures the potential for children from households with low incomes to rise to a higher economic class in adulthood) in their single-family zones. And yet, high-SFZ jurisdictions are inaccessible to families with low incomes who can only afford to live in rental and subsidized housing that these jurisdictions largely exclude through their zoning.

One possible way to advance equity and improve the potential of children from families with low incomes would be to encourage greater residential income integration. Zoning is just one part of that puzzle. States that want to increase income diversity and integration at the jurisdiction level may examine and set a maximum allowable share of land dedicated to single-family zoning, examine patterns of housing tenure, and potentially restructure housing subsidy programs to encourage more rental housing integration in homeowner-dominated neighborhoods. Increasing diversity in jurisdictions’ residential zones is good for income integration and upward social mobility, and states can begin to encourage more diversity with bans or limits on single-family zones.

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Research Areas Neighborhoods, cities, and metros
Tags Families with low incomes Homeownership Housing affordability Housing markets Income and wealth distribution Land use and zoning Multifamily housing Public and assisted housing Racial inequities in neighborhoods and community development Rental housing
Policy Centers Metropolitan Housing and Communities Policy Center
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