He says these are on the rise in many industrial nations with crowded cities and growing pockets of poverty.

他说，这种情况在很多工业化国家里日趋严重，因为这样的国家，城市都很拥挤，生活十分贫困。

That history helps explain the wealth and income gap between blacks and whites, and the concentrated pockets of poverty that persist in so many of today's urban and rural communities.

这段历史有助于解释黑人和白人之间的财富和收入差距，以及当今许多城市和农村社区中持续存在的集中贫困地区。