This paper examines the impact of payment choice on charitablegiving with a door-to-door fund-raising field experiment. Respondentscan donate cash only, use debit only, or have both options. Cash donations have lower visibility vis-a-vis solicitors than debit card donations. When debit replaces...

This paper extends Hotelling's model of price competition with quadratic transportation costs from a line to graphs. I propose an algorithm to calculate firm-level demand for anygiven graph, conditional on prices and firm locations. These graph models of price competitionmay lead to spatial...