One key measure of how well a demographic group is doing is the percentage of children living in communities of high concentrated poverty, in so-called toxic social environments.

There is a rapidly growing body of evidence, compiled by economists, sociologists and public policy experts, which demonstrates the depth of the damage inflicted on children in such toxic neighborhoods.

“Thirty years of research has converged on a clear and compelling fact: It’s not just the family a child is born into that determines her fate, but the neighborhood she grows up in,” Stefanie DeLuca, a sociologist at Johns Hopkins, wrote to me.

DeLuca is one of the authors of a forthcoming book, “Coming of Age in the Other America,” along with Susan Clampet-Lundquist and Kathryn Edin. The book provides evidence that African-American children born in Baltimore’s large public housing projects made significant “educational gains relative to their parents” when their families left the projects, using federally issued housing vouchers to move to privately owned properties.

Reed Jordan, of the Urban Institute, describes in detail how detrimental the effects of impoverished neighborhoods like the constant anxiety

resulting from witnessing and experiencing trauma and violence in distressed neighborhoods, negotiating the sacrifices and trade-offs caused by food insecurity, living in unstable housing conditions, struggling to pay bills, and dealing with numerous other worries burn up cognitive capacity.

Elaborating further, Jordan continues:

Persistent stress and exposure to trauma trigger harmful stress hormones that permanently affect children’s brain development and even their genes. The damage to childhood development is so severe that medical professionals now describe the early effects of poverty as a childhood disease.

Another researcher who has mapped the impact of concentrated poverty is Patrick Sharkey, a sociologist at N.Y.U. Sharkey emailed his findings to me:

If we want to understand why middle-class black Americans are more likely than whites to experience downward mobility, then we should focus on the neighborhoods where blacks and whites have lived for the past 40 years. Blacks making more than $100,000 per year live in more disadvantaged neighborhoods than whites making less than $30,000 per year.

Sharkey points out that

Black children still live in neighborhoods that offer lower quality schools, more toxic stressors like violent crime, more pollution and environmental hazards than white children from similar families. These differences play a big role in explaining racial gaps in economic mobility over the past two generations.

In a 2009 Pew Charitable Trusts report, “Neighborhoods and the Black-White Mobility Gap,” Sharkey argued that:

Neighborhood poverty alone accounts for a greater portion of the black-white downward mobility gap than the effects of parental education, occupation, labor force participation, and a range of other family characteristics combined.

Elizabeth Kneebone, a Brookings Institution scholar, confirms the brutal impact on poor families of concentrated deprivation. In a 2014 essay, “The Growth and Spread of Concentrated Poverty,” she reported that:

The challenges of poor neighborhoods — including worse health outcomes, higher crime rates, failing schools, and fewer job opportunities — make it that much harder for individuals and families to escape poverty and often perpetuate and entrench poverty across generations.

During the 1990s, there was a substantial decline in the percentage of families of all races and ethnicities, including African Americans, living in neighborhoods of dense poverty.