ZIP codes counted. “Every extra year of childhood spent in a better neighborhood seems to matter,” Raj Chetty, a Stanford economist who studied the program, has said. Another researcher, the Harvard economist Lawrence F. Katz, told Retro Report: “Neighborhoods and childhood development are long investments, and one has to have some patience. Most things that are investments take a while to pay off.”

Obviously, segregation in America is a complex matter, historically replete with unsavory practices like redlining and blockbusting, and filled with anger and fear on all sides. Many people, both black and white, are less than enchanted with government efforts at integration that they regard as unwelcome social engineering. Even two of Ms. Morris’s daughters, though beneficiaries of suburban childhoods, found as adults that they felt more at home living in a city.

The face of public housing has changed over the years. In some cities, huge public housing projects have been demolished, including notorious complexes like Cabrini-Green, a Chicago monument to violence, degradation and failure.

But hardships remain. A study last year by the Century Foundation found a sharp increase in “concentrated poverty,” a term applied to a census tract where at least 40 percent of the residents are below the federal poverty line — about $24,000 for a family of four. From 2000 to 2013, the foundation said, the number of Americans living in concentrated poverty rose to 13.8 million from 7.2 million, with African-Americans and Latinos disproportionately represented. In major cities like Chicago, Detroit, Milwaukee and Baltimore, daily life is racially separate and decidedly unequal.

Subsidized housing is not the only element in America’s racial mosaic, but it looms large. The Housing Choice Voucher Program, run by the Department of Housing and Urban Development, assists about 2.4 million families with a total of 5.3 million people. Households typically apply 30 percent of their income to the rent, with the government paying the rest.

HUD calculates what it judges to be “fair-market rent” for a broad metropolitan region — a method that, however unintentionally, provides many poor families with subsidies sufficient to lift them into only marginally better neighborhoods, if that. Moving to appreciably more prosperous areas is often impossible.

This is where the Obama administration steps in. Its HUD secretary, Julián Castro, wants to fine-tune how fair-market rent is calculated, by basing it on housing costs in individual ZIP codesrather than in entire regions. Under this methodology, people who find an apartment in a higher-rent zone would have their subsidy increased substantially. A system like this was tried in Dallas, reportedly with fair success.

There is a potential downside: Families that remain in neighborhoods where rents are comparatively low would find their vouchers cut, a prospect that has produced objections from some elected officials, including in New York. They warn that if those subsidies shrink, some poor families will have to pay more out of their own threadbare pockets or be forced to move.

A final decision by HUD is expected this fall. But it is already clear that if there is a constant in life’s game of Chutes and Ladders, it is the consuming importance of one’s ZIP code. No one knows that better than Henry G. Cisneros, the HUD secretary during the Clinton years.

“All of the other forms of segregation that exist in our society,” Mr. Cisneros told Retro Report, “begin with, ‘Where do you live?’”

CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.

This article first appeared in The New York Times.