Can consumer surplus decrease with merger efficiencies?

This paper investigates the impact of mergers on consumer welfare within a Cournot model, considering mergers driven by anticipated efficiency gains and potential post-merger entry. In this framework, we demonstrate that: (i) modest efficiencies can make both merger and entry beneficial, benefiting consumers; (ii) moderate efficiencies may deter entry, harming consumers due to the merger; and (iii) significant efficiencies may discourage entry but lead to lower prices, benefiting consumers. This result, therefore, embodies an important policy implication that assessing the overall effect of a merger on consumer surplus requires evaluating merger-specific synergies alongside the likelihood of post-merger entry.