Why Do The Poor Live In Cities?

Here is the abstract for an interesting paper by Glaeser, Kahn & Rappaport:

"More than 17 percent of households in American central cities live in poverty; in American suburbs, just 7.4 percent of households live in poverty. The income elasticity of demand for land is too low for urban poverty to be the result of wealthy individuals' wanting to live where land is cheap (the traditional urban economics explanation of urban poverty). Instead, the urbanization of poverty appears to be the result of better access to public transportation in central cities, and central city governments favoring the poor (relative to suburban governments)."