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...

In many markets, user benefits depend on participation and usage decisions of other users giving rise to network effects. Intermediaries manage these network effects and thus act as platforms that bring users together. This paper reviews key findings from the literature on network effects and...

We study optimal merger policy in a dynamic model in which the presence of scale economies implies that firms can reduce costs through either internal investment in build- ing capital or through mergers. The model, which we solve computationally, allows firms to invest or propose mergers...

We develop a model of interlocking bilateral relationships between upstream firms (manufacturers)that produce differentiated goods and downstream firms (retailers) that compete imperfectly for consumers. Contract offers and acceptance decisions are private information to the contracting parties....

We study welfare effects of horizontal mergers under a successive oligopoly model and find that downstream mergers can increase welfare if they reduce input prices. The lower input price shifts some input production from cost- inefficient upstream firms to cost-efficient ones. Also, the lower...

We customize the aggregative game approach to oligopoly to study asymmetric media markets. Advertiser, platform, and consumer surplus are tied together by a simple summary statistic. When media are ad-financed and ads are a nuisance to consumers we establish see-saws between consumers and...

It has been suggested that mergers, by increasing concentration, raise incentives to invest and hence are pro-competitive. To study the effects of mergers, we rewrite a game with simultaneous price and cost-reducing investment choices as one where firms only choose prices, and make use of...

We study the relationship between collusion and corruption in a stylized model of repeated procurement where the cost of reporting corrupt bureaucrats gives rise to a free riding problem. As in Dixit (2015, 2016), cooperation among honest suppliers alleviates free-riding in reporting. However,...