Either or Both Competition: A "Two-Sided" Theory of Advertising with Overlapping Viewerships

In media markets, consumers spread their attention to several outlets, increasingly so as consumption migrates online. The traditional framework for competition among media outlets rules out this behavior by assumption. We propose a new model that allows consumers to choose multiple outlets and use it to study the effects on advertising levels and the impact of entry and mergers. We identify novel forces which reflect outlets' incentives to control the composition of their customer base. We link consumer preferences and advertising technologies to market outcomes. The model can explain several empirical regularities that are difficult to reconcile with existing models.