This paper analyzes a model in which owners of competing firms can hire biased managers for strategic reasons. We show that independent of the mode of competition, that is, price or quantities, owners hire aggressive managers. This result contrasts with the classic literature on strategic delegation.

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. (JEL D42, D43, L12, L13, L82, L86, M37)

The existing literature on "two-sided markets" addresses participation externalities, but so far it has neglected pecuniary externalities between competing platforms. In this paper we build a model that incorporates both externalities. In our setup differentiated platforms compete in advertising and offer consumers a service free of charge (such as a TV program) that is financed through advertising. We show that advertising can exhibit the properties of a strategic substitute or complement. Surprisingly, there exist cases in which platforms benefit from market entry. Moreover, we show that from a welfare point of view perfect competition is not always desirable. JEL-classification numbers: D43, L13, L82

We develop a model of successive oligopolies with endogenous entry, allowing for varying degrees of product differentiation and entry costs in both markets. We show that downstream conditions dominate the overall profitability of the two‐tier structure while upstream conditions mainly affect the distribution of profits. We analyze how two‐part tariffs and resale price maintenance shape the endogenous market structure and study their welfare effects. In contrast to previous literature, we find that welfare under linear prices can be larger than under twopart tariffs although the latter avoids double marginalization. This is because linear prices induce more downstream market entry.

For many products, platforms enable sellers to transact with buyers. We show that the competitive conditions among sellers shape the market structure in platform industries. If product market competition is tough, sellers avoid competitors by joining different platforms. This allows platforms to sustain high fees and explains why, for example, in some online markets, several homogeneous platforms segment the market. Instead, if product market competition is soft, agglomeration on a single platform emerges, and platforms fight for the dominant position. These insights give rise to novel predictions. For instance, market concentration and fees are negatively correlated in platform industries, which inverts the standard logic of competition.