'The number of people living in neighborhoods of extreme poverty grew by a third over the past decade, according to a new report, erasing most of the gains from the 1990s when concentrated poverty declined.

More than 10 percent of America’s poor now live in such neighborhoods, up from 9.1 percent in the beginning of the decade, an addition of more than two million people, according to the report by the Brookings Institution, an independent research group.

Extreme poverty — defined as areas where at least 40 percent of the population lives below the federal poverty line, which in 2010 was $22,300 for a family of four — is still below its 1990 level, when 14 percent of poor people lived in such areas.

...In 'The Truly Disadvantaged,' William Julius Wilson, a sociologist now at Harvard who pioneered the concept, argued that residents of such areas were more likely to experience joblessness, poor schools, broken families and high crime.

Living in such areas often led to poorer health and educational outcomes for children, creating higher hurdles for success as adults.

'It’s the toughest, most malignant poverty that we have in the United States,' said Peter Edelman, the director of the Center on Poverty, Inequality and Public Policy at Georgetown University. 'It’s bad outcomes reinforcing each other.'