Romantic interest on swipe-based dating apps (SBDAs) is highly concentrated. This can frustrate both popular users who feel overwhelmed by a glut of attention, and less popular users who feel dejected by a lack of it. Is the concentration of interest exacerbated by the platform design of dating apps? I provide causal evidence on the effects of two common design features – the emphasis on visual elements in profiles,and limits on the number of profiles users can express interest in – on the concentration of interest (“likes”), and show that both, as implemented under the status quo,concentrate interest. To do so, I design, build, and run my own experimental dating app, which closely resembles conventional SBDAs and allows participants to form real matches. Across three field experiments, over 1,000 participants use the app to makeover 70,000 matching decisions.…