Homelessness has been on the rise in virtually all large cities, including Los Angeles, New York, and San Francisco, even as it declines elsewhere. Despite numerous exposés on the growth of suburban poverty, the poverty rate in core cities remains twice as high; according to the 2010 census, more than 80 percent of all urban-core population growth in the previous decade was among the poor. For all the talk about inner-city gentrification, concentrated urban poverty remains a persistent problem, with 75 percent of high-poverty neighborhoods in 1970 still classified that way four decades later.

Clearly, then, the urban renaissance has not lifted all, or even most, boats. San Francisco, arguably the nation’s top urban hot spot, is seeing the most rapid increase in income inequality of any metropolitan area in the nation, according to a Bloomberg study. The ranks of the country’s most bifurcated cities include such celebrated urban areas as San Francisco, New York, Chicago, and Los Angeles, where the poverty rate is higher now than before the 1992 riots, both in the city proper and in the riot zone.

The new urban demographic—a combination of poor residents, super-affluent households (many childless), and a younger generation with limited upward mobility—has created conditions peculiarly ideal for left-wing agitation.