Economics of collective refusals to supply

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This paper examines situations where vertically integrated firms refuse to supply an input to an independent competitor in the downstream market. The treatment of such cases by competition or regulatory authorities is often based on the assumption that such outcomes can only arise if there is collusion in the upstream markets. We argue that this is not always the case. In particular, we argue that proper antitrust or regulatory assessment of such cases must take into account the nature of competition, whether sales contracts are observable, the degree of contractual flexibility that is permitted, the substitutability of downstream products, and even the number of potential competitors in the downstream market.