Endogenous Mergers in Vertically Differentiated Markets

This paper studies the incentives for firms competing in vertically differentiated markets to sign binding collusive agreements, as in the case of mergers and alliances. Empirical investigations show that firms involved in mergers and acquisitions revise prices and qualities as to maximize their joint profits. In a few cases merging firms are also observed shutting down some lines of activities (so called market pruning). In this paper we attempt to test these predictions by modelling a three-stage game in which, at the first stage, three firms selling goods independently in a vertically differentiated market can commit to sign either a full or a partial voluntary agreement (with a subset of firms) via a sequential game of coalition formation while, at the second and third stage they can optimally revise their qualities and prices, respectively. In such a setting we study whether some binding agreements (as full or partial mergers) can be sustained as subgame perfect equilibria of the coalition formation game. Moreover, we analyse the final effects of different coalition structures on equilibrium qualities, prices and profits accruing to firms. We obtain the following results: (i) initial firms' heterogeneity appears a crucial factor for mergers to arise; (ii) although profitable, the grand coalition of firms (i.e. the whole market merger) is not the outcome of the finite-horizon negotiation, where only partial mergers arise; (iii) all stable mergers comprehends the firm producing the bottom quality good; (iv) all stable mergers reduce the number of variants on sale (market pruning); (v) stable mergers always increase the quality gap among variants. All model findings seem compatible with the existing empirical observations.