Damian: Yes, that’s certainly true of Paris (and has been, to some extent, for a very long time, though it might have become worse over the past twenty years). I think the rich city/poor suburb pattern is much more common in Europe than here, but of course in most European conurbations, social welfare programs are extensive, income inequality is less extreme, and there is ample public transportation, so the economic effects of any displacement are less painful.

Another possibility is to have cities demand that all high-density housing in desirable, central areas be mixed income–such that not every unit is ‘luxury.’ But then we are faced with the ugly social and psychological fact that having mixed-income or mixed-race buildings would likely drive down the value of their higher-end units.

Governments could try to encourage middle income coops, like the late ’40s one I live in in NYC. But the unions organized mine and it’s unclear to me who would do so today.

Recently, my suspicion is that those who want urban living and are priced out of NYC or Chicago, might seek out smaller cities (like Portland, ME, or Scranton, or Lexington, KY) that are affordable, where they may be able to float up on the rising tides of urban real estate prices.