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In repeated normal-form (simultaneous-move) games, simple penal codes (Abreu, 1986, 1988) permit an elegant characterization of the set of subgame-perfect outcomes. We show that the logic of simple penal codes fails in repeated extensive-form games. By means of examples, we identify two types of settings in which a subgame-perfect outcome may be supported only by a profile with the property that the continuation play after a deviation is tailored not only to the identity of the deviator, but also to the nature of the deviation. Download Paper
We investigate the impact of vertical mergers on upstream firms' ability to sustain tacit collusion in a repeated game. We identify several effects and show that the net effect of vertical integration is to facilitate collusion. Most importantly, vertical mergers facilitate collusion through the operation of an outlets effect: cheating unintegrated firms can no longer profitably sell to the downstream affiliates of their integrated rivals. However, vertical integration also gives rise to an opposing punishment effect: it is typically more difficult to punish an integrated structure, so that integrated firms are able to make more profits in the punishment phase than unintegrated upstream firms. When downstream firms can condition their prices or quantities on upstream firms' contract offers, two additional effects arise, both of which further facilitate upstream collusion. First, an unintegrated upstream firm's deviation profits are reduced by the reaction effect which arises since the downstream unit of the integrated firm will now react aggressively to upstream deviations. Second, an integrated firm's deviation profit is reduced by the lack-of-commitment effect as it cannot commit to its own downstream price when deviating upstream. Download Paper
In repeated normal-form games, simple penal codes (Abreu 1986, 1988) permit an elegant characterization of the set of subgame-perfect outcomes. We show that the logic of simple penal codes fails in repeated extensive-form games. We provide two examples illustrating that a subgame-perfect outcome may be supported only by a profile with the property that the continuation play after a deviation is tailored not only to the identity of the deviator, but also to the nature of the deviation. Download Paper
In this paper we investigate the impact of vertical mergers on upstream firms' ability to sustain collusion. We show in a number of models that the net effect of vertical integration is to facilitate collusion. Several effects arise. When upstream offers are secret, vertical mergers facilitate collusion through the operation of an outlets effect: Cheating unintegrated firms can no longer profitably sell to the downstream affiliates of their integrated rivals. Vertical integration also facilitates collusion through a reaction effect: the vertically integrated firm's 'contract' with its downstream affiliate can be more flexible and thus allows a swifter reaction in punishing defectors. Offsetting these two effects is a possible punishment effect which arises if the integrated structure is able to make more profits in the punishment phase than a disintegrated structure. Download Paper