A key reason for the existence of cities are the externalities created when people cluster together in close proximity. During Covid, such interactions came with health risks and people found other ways to interact. We document how cities changed during Covid and consider how the persistence of...

This paper studies social-tie formation when individuals care about the geographical location of other individuals. In our model, the intensity of social interactions can be chosen at the same time as friends. We characterize the equilibrium in terms of both social interactions and social...