Multihoming and Oligopolistic Platform Competition

We provide a general framework to analyze competition between any number of symmetric two-sided transaction platforms, in which buyers and sellers can multihome. We show how key primitives such as the number of platforms, the fraction of buyers that find multihoming costly, the value of transactions, and the degree of user heterogeneity jointly determine the level and structure of platform fees. Even though platform entry always reduces the total fee level, whether it shifts the fee structure in favor of buyers or sellers depends on whether most of the buyers are singlehoming or multihoming. (JEL D43, L11, L13, L40)