Horizontal Mergers Under Asymmetric Information About Synergies

This paper analyses a situation in which there are three quantity‐setting firms, two of which are considering whether or not to merge. When these two firms have private information about the potential cost‐saving synergies of the merger, they may have an incentive to overstate them. This is because if they succeed in making the non‐merging rival firm believe that the synergies are high, the rival firm reduces output and the merger becomes more profitable. Under some conditions, anticipating that the rival will form such a belief, low‐synergy firms that would never merge under complete information will mimic high‐synergy firms by merging. Such pooling behaviour by the merging firms can have a negative impact on social welfare.