The striking economic agglomerations emerging in affluent democracies are generating, reproducing, and expanding inequalities. A major mechanism for this is housing, which is both a repository for wealth and, under these conditions, a magnifier of wealth. Access to urban areas – the site of educational, labor, and marriage market advantages – is contingent upon access to housing. We use comparative analysis of cases in Europe (London and Paris) and the United States (New York and San Francisco) to consider the capacities of different societies to limit or ameliorate these new sources of diverging opportunity. These seemingly local issues remain shaped by distinct national political contexts, which vary dramatically in their capacity to support local affordable housing and reduce the collective action problems confronting major metropolitan areas.