Rationalizability and Efficiency in an Asymmetric Cournot Oligopoly.

We study rationalizable solutions in a linear asymmetric Cournot oligopoly. We show that symmetry across firms favors multiplicity of rationalizable solutions: A merger (implying a greater asymmetry across firms) makes out-of-equilibrium behavior less likely and should dampen &lquo;coordination&rquo; volatility. The market structure maximizing consumers' surplus at a rationalizable solution is not always the competitive one: This may be a symmetric oligopoly with few firms. An empirical illustration to the airlines industry shows that a reallocation of 1% of market share from a small carrier to a larger one yields a 1.3% decrease in volatility, measured by the within carrier standard error of the number of passengers.