CAMBRIDGE, MASS. Advocates for the poor have protested President Bush's $350 billion tax cut on many grounds, notably its selective use of the per-child tax credit. But few have discussed its potential effect on one of the more remarkable long-term economic trends of the last decade: the decline in concentrated poverty in America.

A recent report for the Brookings Institution by a University of Texas social scientist, Paul Jargowsky, revealed that the number of people residing in high-poverty neighborhoods decreased by 24 percent, or 2.5 million people, from 1990 to 2000. Moreover, the number of such neighborhoods — the study defined them as census tracts with at least 40 percent of residents below the poverty level — around the country declined by more than a quarter.

The news has been greeted as a major step forward for inner-city blacks, because their neighborhoods tend to feature the highest levels of concentrated poverty. To some extent this is true, although perhaps not in the way either the political left or right are spinning it. And, as promising as the findings are, they do not signify that we've found a magic bullet in the war on poverty.

In fact, the study conforms to the long-held if oft-ignored fact that the state of America's urban core is not separate from that of the country's economy as a whole. Thus the notable reduction in the number of high-poverty neighborhoods, and the substantial decrease in the population of such neighborhoods, may simply be blips of boom times rather than permanent trends.

Social scientists have rightly devoted considerable attention to concentrated poverty because it magnifies the problems associated with poverty in general: joblessness, crime, delinquency, drug trafficking, family breakups and poor "social outcomes" like school performance. Moreover, as Mr. Jargowsky has emphasized in previous research, when high poverty rates spread through a neighborhood, middle- and working-class people tend to see the area as "dangerous." It becomes isolated, socially and economically, as people go out of their way to avoid it.

In 1990 almost a third of blacks lived in such neighborhoods; the 2000 figure was 19 percent. Yet despite this significant improvement, African-Americans still have the highest rates of concentrated poverty. In part, the state of inner-city ghettoes is a legacy of historic racial subjugation. And it is true that racial discrimination and segregation continue to play a role in limiting the progress of many African-Americans.

However, neither the spectacular rise in black concentrated poverty from 1970 to 1990, nor the dramatic decline from 1990 to 2000, can be explained mainly in terms of race. Rather, these shifts demonstrate that the fate of African-Americans and other racial groups is inextricably connected with changes across the modern economy.

The data bear this out. The declines in concentrated poverty in the 90's occurred not just in a few cities but across the country. Virtually all racial and ethnic groups recorded improvements. The number of whites living in these neighborhoods declined by 29 percent (from 2.7 million people to 1.9 million), and the number of blacks decreased by 36 percent (from 4.8 million to 3.1 million). For all races, the greatest improvements against poverty concentration were in the South and Midwest, the smallest in the Northeast, mirroring wider economic trends.

Nonetheless, there is a tendency among scholars, black leaders and policy makers to view the economic problems in the African-American community, including the growth of concentrated poverty, separately from national and international trends affecting all American families and neighborhoods. One reason may be a desire for tidy solutions. However, if the economic problems of the black community are defined exclusively in terms of race, they can be isolated and seen as requiring only race-specific solutions, as proposed by the political left, or narrow political solutions with subtle racial connotations (like welfare reform), as trumpeted by the right.

A look at the long-term statistics shows that neither welfare reform nor race-based programs seems to have had much to do with changes in poverty concentration. The sharp rise in concentrated poverty occurred during a period of rising income inequality for all Americans that began in the early 1970's. This was a period of decline in inflation-adjusted average incomes among the poor and of growing economic segregation caused by the exodus of middle-income families from inner cities. What had been mixed-income neighborhoods were rapidly transformed into areas of high poverty.

Almost 30 years ago, the African-American economist Vivian Henderson pointed out that "the economic future of blacks in the United States is bound up with that of the rest of the nation." So, just as blacks suffered greatly during the decades of growing separation between haves and have-nots, they benefited considerably from the incredible economic boom in the last half of the 1990's, which not only substantially reduced unemployment, including black unemployment, but sharply increased the earnings of all low-wage workers as well.

Undoubtedly, if the robust economy could have been extended for several more years, rather than coming to an abrupt halt in 2001, concentrated poverty in inner cities would have declined even more.

This cannot be proved now; data on concentrated poverty are provided only by the decennial census. But the Brookings report clearly shows that the favorable trend of the 1990's may be temporary rather than long term. Unemployment and individual poverty rates are on the rise again; more than 2.4 million jobs have disappeared in the last two years. And given the continuing increase in the Hispanic population, the number of high-poverty barrios is likely to grow rapidly in a sluggish economy.

That is why my concern extends beyond the details of Mr. Bush's tax cuts to the big picture. If, as many economists predict, the cuts result in huge budget deficits and further weaken a faltering economy, we may again see the depressingly high levels of concentrated poverty recorded in 1990.

The lesson for those committed to fighting inequality, especially those involved in multiracial coalition politics, is to pay more scrutiny to fiscal, monetary and trade policies that may have long-term consequences for the national and regional economies, as seen in future earnings, jobs and concentrated poverty. We must remember that high-poverty neighborhoods reflect America, all of America.

William Julius Wilson, professor at Harvard's John F. Kennedy School of Government and department of African and African-American studies, was awarded the National Medal of Science in 1998.

Copyright 2003 The New York Times Company. Reprinted from The New York Times, OP-ED, of June 16, 2003.