As the first decade of the 21st century comes to a close, more black, Asian, Hispanic, foreign-born and poor people live in the suburbs of the nation's largest metropolitan areas than in their primary cities. 'Several trends in the 2000s further put to rest the old perceptions of cities as declining, poor, minority places set amid young, white, wealthy suburbs,' a report released Sunday by the Brookings Institution concluded. That demographic inversion was accompanied by another first since the 2000 census: In the nation's 100 largest metropolitan areas, black, Hispanic and Asian residents constitute a majority of residents younger than 18 -- presaging a benchmark that the nation as a whole is projected to reach in just over a decade. With the first decade of the century nearly over, the number of married couples fell to fewer than half of the nation's households, and the wage gap between rich and poor was the highest recorded in modern times (the 2010 census will apparently be the first in which the inflation-adjusted median household income will have declined over the decade). Meanwhile, the aging population was producing both a cultural generation gap between elderly whites and younger nonwhite residents and a surfeit of single people in the suburbs. The Brookings preview of the 2010 census results for the largest metropolitan areas was accompanied by a plea for a national urban agenda that addresses the challenges posed by a changing population. Among its suggestions were placing a price on carbon emissions, discouraging an 'over-consumption' of housing by reducing deductibility of mortgage interest, providing a pathway to legal status for illegal immigrants, improving teacher training and expanding tax credits to narrow income inequality. 'We can't address this piecemeal,' said Judith Rodin, the president of the Rockefeller Foundation, which financed the study. 'Demographic change and coping with the results of that change are beyond the capacity of local actors,' said Alan Berube, research director of Brookings' Metropolitan Policy Program, directed by Bruce Katz. The 'State of Metropolitan America' report echoed other evidence of disparities among ethnic and racial groups. Last month, the American Human Development Project, a nonpartisan research group, found, for example, that Asians in New Jersey live an average of 26 years longer and are 11 times as likely to have a graduate degree than American Indians in South Dakota. 'The seeds of new racial and ethnic competition for public resources have been planted as a result of decadelong race-ethnic shifts,' said William Frey, a Brookings demographer. In Arizona, which adopted a tough law last month giving the police broad discretion to question people about their immigration status, whites account for 83 percent of the population older than 65, but only 43 percent of those 18 and younger. That gap is greatest in Arizona, Frey said, but California, Florida, Nevada, New Mexico and Texas are not far behind. 'When inequities, disparities and suspicion grow, political problems accelerate,' Rodin said. 'Today it's about immigration. Tomorrow it could be about wages or jobs.' The report defines suburbs as all of a metropolitan area outside its primary city. Some suburbs have been growing more diverse for decades; Asian and Hispanic suburbanites made up a majority in metropolitan areas even before 2000. At the same time, since 2000 the white population grew in a number of central cities, including Atlanta and New York. Immigration slowed some since 2000. In older gateways like New York and San Francisco, immigrants in the primary city outnumber those in the suburbs, but not in newer magnets like Atlanta and Las Vegas. By continent, Africans were the fastest-growing immigrant group. Fewer Americans moved from one house to another since 2007 than at any time since World War II, a phenomenon attributed to the recession. The share of Americans commuting by public transit rose, marginally, for the first time in decades. States of the 'Old South' accounted for 57 percent of the nation's black population in 2008, compared with 54 percent in 1990. Fully one-fifth of the metropolitan gains in black population since 2000 occurred in Atlanta, pushing it past Chicago for the second-largest black population, behind New York. Older areas like Pittsburgh, experienced precipitous drops in the number of married couples with children -- leaving those cities with nearly half their population at 45 and older. Since 2000, the number of 55- to 64-year-olds nationwide grew by nearly 50 percent. Next year, the first baby boomers turn 65. By 2008, nonfamilies -- mostly single people living alone, but also some unmarried partners without children -- emerged as the most prominent suburban household. Among every racial and ethnic group, suburbs are still the place where most married couples live. But half the suburbs registered declines in the share of married-couple households. Racial and ethnic minorities now account for a majority of the population in 17 metropolitan areas, most of them in California and Texas although New York, at 50.7 percent in 2008, is poised to pass that threshold in the 2010 census. Asians made up 5 percent or more of the population in 22 of the largest metropolitan areas by 2008, compared with 9 in 1990. Since 2000, 26 metropolitan areas became at least 5 percent Hispanic, and an additional 10 areas passed 10 percent. The Brookings report is drawn from census and other data through 2008. Except for income figures that will reflect the depths of the recession, few trends identified so far during the decade appear likely to be reversed by more recent census results. Nearly all the figures relate to the largest metropolitan areas, which were at the vanguard of demographic change. The 100 biggest grew by about 28 million people since 2000. They are now home to two-thirds of the nation's population. 