Demographics aren’t just about identity. They’re about how and where different populations interact. Social infrastructure is the network of physical spaces and institutions — from sidewalks to public parks, libraries to cafes — that, when robust, promote community-building activities among otherwise diverse clans. When these resources are degraded, however, they discourage interaction, leaving different demographic groups — however you define them — to fend for themselves. The stakes are real: Weak social infrastructure breeds economic isolation, political misunderstanding, and the social divisions that fuel the most dangerous forms of xenophobia. Particularly in the wake of the recent U.S. election, the need for public and private investment in this infrastructure couldn’t be more urgent.