My neighbor next floor: the built environment and social preference

We assess the effect of the built environment on low-cost helping behavior toward neighbors. The setting is communities in Shanghai, China that, due to rapid development, were involuntarily relocated to different building structures. Our natural field experiment accounts for potential misreporting, attrition, and interference. Treatment assignment avoids interference by design, and we develop a randomization test to account for the bias this introduces. Living one floor apart reduces the willingness to help a neighbor by 20 percentage points, as does adding one more apartment per floor. Small spatial barriers can profoundly shape social interactions, and helping behavior, in urban settings.