Standard economics provides a well-understood framework of the competitive determinants of market prices that is now widely accepted for antitrust analysis. In “two-sidedmarkets,” where firms supply products demanded by two interrelated groups of consumers, these competitive forces operate...

In framework of Rochet and Tirole (2011), I allow for partial merchant internalization and study how MIT threshold is related to levels of inter-change fee that maximize various components of social welfare. I find that cost absorption on the side of issuers and merchant heterogeneity each bias...