This paper proves the existence and uniqueness of Cournot equilibrium in models of international trade under oligopoly. The existence of Cournot equilibrium is established without the usual assumption that profit functions are concave. Instead the proof uses a weaker "aggregate concavity"...

The analysis of collusion in infinitely repeated duopoly games has generally assumed that marginal cost is constant, but this note uses quadratic costs (linear marginal costs) to compare the sustainability of collusion under Bertrand and Cournot duopoly with differentiated products. It is shown...