This dissertation consists of two essays. The connecting theme for this body of work is social interaction. I define social interaction, for this dissertation, as non-market based face-to-face interaction between individuals where each is interested in a response. The first contribution investigates the relationship between social interaction and neighborhood population density. I use the exogenous variation in a set of geological instruments to predict the neighborhood population density. The results suggest that an increase in neighborhood population density increases some types of social interaction. The second contribution brings social interaction into a standard urban consumer theory model, the Alonso-Muth model
