This note describes the implementation of the hypothetical monopolist ssnip test for market definition in the context of merger cases where firms produce multiple differentiated products. The test developed here represents an extension and generalization of the Katz-Shapiro and...

In this short and mainly expository article, we explain the “hypothetical monopolist test” that has become the standard methodology for identifying relevant antitrust markets in merger cases, and discuss two approaches to implementing the test. We then focus on the implementation of the test...

One key concern in vertical merger cases is input foreclosure. Input foreclosure involves raising the costs of competitors in the downstream market, which could in turn increase the sales and profits of the downstream merger partner. In this article, we explain how the upward pricing pressure...

These comments (originally submitted to the DOJ and FTC in November 2009) make a number of comments relevant to revising the Merger Guidelines. The comments focus on the use of the GUPPI (gross upward pricing pressure index) in unilateral effects analysis. They also comment on the deterrence and...

We present a model of ordered bargaining between one buyer and several sellers, with Nash bargaining at each stage. We first show that the model has the property that the buyer's payoff equals the expected utility of a weighted sum of independent Bernoulli random variables. We then exploit this...

This paper explores cooperation incentives in the absence of public reputation information, using an infinite-horizon Prisoners' Dilemma model of sequential relationships. We examine a strategy which we call Quit-for-Tat (QFT). In this model, individuals initially are paired randomly. In the...

The 2010 Merger Guidelines give greater prominence to the concept of parallel accommodating conduct. Parallel accommodating conduct (PAC) has a long history in oligopoly theory, dating back more than seventy years. It is a type of coordinated conduct that does not require an agreement. Instead,...