Duopoly signal jamming

Summary This paper examines a repeated duopoly market with heterogeneous outputs. Firms have (common) prior beliefs over the values of an unknown parameter of each firm's demand curve. Firms cannot observe rivals' quantities, but can observe market prices, which are subject to random disturbances and hence provide noisy information that firms use to update their beliefs concerning the unknown parameters' values. Each firm can potentially signal jam, or strategically vary its output level in order to manipulate the distribution of likely market prices and hence the likely inferences drawn by the opponent. We find that the opportunity to signal-jam introduces two conflicting effects, arising out of the desire to manipulate expectations concerning each of the two demand curves. Depending upon the relative magnitudes of these two effects, signal-jamming may lead firms to either increase or decrease period-one quantities. If the firms are symmetric, then the opportunity to signal jam induces both firms to increase output in order to induce their rival to conclude that demand is unfavorable. However, if the firms believe almost surely that one of the possible parameter values is true for firm 2's demand curve (for example), then firm 1 may signal-jam by producing less output.We thank two anonymous referees, an associate editor and Pieter Kop Jansen for helpful comments that corrected some errors. Larry Samuelson is grateful to the Center for Economic Research at Tilburg University and the Department of Economics at the University of Bonn for support. Financial support by the Deutsche Forschungsgemeinschaft (DFG) through Sonderforschungsbereich 303 is gratefully acknowledged.