Downstream mergers in a vertically differentiated unionized oligopoly

In the context of an international unionized oligopoly, with vertical differentiation and downstream and upstream firms locked in a bilateral monopoly, the pattern of downstream mergers is investigated. In such a setting, a downstream merger leads to a reduction in the price of the inputs. Such reduction is greater the more homogeneous the participants’ products are. However, it turns out that most of the market structure equilibria consist of mergers among differentiated producers. I find that firms’ strategic behaviour impedes mergers between similar producers, avoiding that input prices fall to their marginal costs. Given that firms can be harmed by rivals’ mergers, through the important reduction in input prices that those trigger, an scenario of preemptive mergers emerges. A brief social welfare analysis is also presented. It is shown that the market structure outcome is never socially optimal, neither in terms of consumer surplus nor social welfare. Nevertheless, the optimum could be achieved if antitrust authorities block some strategic mergers, precisely those involving more than two firms.