This essay surveys the economic literature on interchange fees and the debate over whether interchange should be regulated and, if so, how. We consider, first, the operation of unitary payment systems, like American Express, in the context of the recent economic literature on two-sided markets,...

We apply and extend the cost-based approach to bundling and tying under competition developed in Evans and Salinger (2004a) to over-the-counter pain relievers and cold medicines. We document that consumers pay much less for tablets with multiple ingredients than they would to buy tablets with...