America’s most affluent neighborhoods are worlds apart from its most disadvantaged ones, and the gap has grown in the past two decades. How much of that change happened within the same neighborhoods—that is, how many of the neighborhoods at the top in 1990 stayed at the top, as even richer versions of themselves, in 2010? What about the bottom neighborhoods? Did they get stuck too?

Until recently, it’s been tough to answer questions like these because the Census Bureau redraws its neighborhood boundary definitions every 10 years. But Urban’s Neighborhood Change Database, built with support from the Rockefeller Foundation, allows us and many other researchers to learn about how, whether, and why neighborhoods evolve because it reconciles boundaries and data definitions over time.

Some neighborhoods are locked in to disadvantage—or privilege

Policymakers and researchers have been concerned recently about the extent to which distressed neighborhoods stay that way over time—that is, they get “locked in” to disadvantage by a cycle in which investment lags, crime grows, and households and businesses flee when they have a chance to find a better location.

Our research bears out this concern. We ranked each commuting zone’s tracts based on income, housing value, homeownership rates, and college education rates. Of the bottom 10 percent of neighborhoods in 2010, more than three-fifths (62 percent) were already bottom tracts in 1990. Among the large commuting zones, lock-in at the bottom was most pronounced in slow-growth, racially segregated commuting zones. In Baltimore, Boston, Bridgeport, Buffalo, Detroit, Milwaukee, Philadelphia, and St. Louis, between 70 and 80 percent of the bottom tracts in 2010 were also bottom tracts in 1990.

Overall, the tracts in the 570 commuting zones we analyzed gained almost 50 million residents from 1990 to 2010. But the bottom tracts grew by fewer than 30,000 people over that period, and almost 40 percent lost at least 10 percent of their population.

What about the top tracts? Here, lock-in is even more pronounced: a full two-thirds of the 2010 top tracts (the highest-ranking 10 percent of tracts) were already in the top 10 percent in 1990. In 108 commuting zones, over 80 percent of the top tracts in 2010 were also top tracts in 1990. Only 75 commuting zones had this level of lock-in for bottom tracts. All the commuting zones with high lock-in at the bottom also had high levels at the top, but a few other high-income commuting zones—San Jose, Seattle, Los Angeles, New York, and Washington, DC, for example—were also among those in which over 70 percent of the top neighborhoods in 2010 had already become top neighborhoods by 1990.

How the top tracts stay on top

A web of self-reinforcing policies and practices protect the position of top neighborhoods in their metropolitan areas. Many wealthier neighborhoods use zoning to keep apartments out and purchase open space to limit development further. In many states, they incorporate as separate municipalities to control school districts and tax rates. In suburban areas, they reject investment in roads, water supplies, and sewers as a way to limit growth—especially growth at densities high enough to support rental housing.

States often condone or reinforce these local exclusionary practices. In the mid-2000s, for example, Maryland—home to some of the nation’s most privileged neighborhoods—required local governments to approve in advance all applications for federal low-income housing tax credits. While this policy was in effect, the share of projects built with the credit in low-poverty neighborhoods fell by 17 percentage points. (Maryland has since changed this policy.)

Lock-in among high-opportunity neighborhoods is one reason why the recently issued Affirmatively Furthering Fair Housing rule is so important. It requires state and local governments to allow developers to meet market demand for affordable rental housing by changing their exclusionary policies. When low-income people live in better and safer neighborhoods, with greater access to high-quality public services and private goods, it will improve their health and their children’s earning potential. Indirectly, then, reducing lock-in could even contribute to national economic growth.