Alliance Formation in a Vertically Differentiated Market

This paper studies how the possibility for firms to sign collusive agreements (as for instance being part of alliances, cartels and mergers) may affect their quality and price choice in a market with vertically differentiated goods. For this purpose we model the firm decisions as a three-stage game in which, at the first stage, firms can form an alliance via a sequential game of coalition formation and, at the second and third stage, they decide simultaneously their product qualities and prices, respectively. In such a setting we study whether there exist circumstances under which either full or partial collusion can be sustained as a subgame perfect Nash equilibrium of the coalition formation game. Also, we analyse the effects of different coalition structures on equilibrium qualities, prices and profits accruing to firms. It is shown that only intermediate coalition structures arise at the equilibrium, with the bottom quality firm always included. Moreover, all equilibrium price and quality configurations always coincide with that observed in the duopoly case, with only two quality variants on sale.