Is Most Poverty "Concentrated" Poverty?

A new publication on poverty from the Century Foundation includes this statement:

Poverty levels have proved to be so difficult to reduce largely because poor people tend to be isolated in neighborhoods that predominantly consist of other poor people.

Economic isolation and segregation is certainly a problem, but it isn't actually the case that most people living below the official poverty line live in neighborhoods that predominately consist of people living below the poverty line. In fact, as this Urban Institute report shows, a majority of people with below-poverty incomes live in neighborhoods in which fewer than 20 percent of the residents have below-poverty incomes.