Merger control authorities may approve a merger based on an “efficiency defense.” An important aspect in clearing mergers is that the efficiencies need to be merger-specific . Joint ventures, and in particular research joint ventures (RJVs), may achieve comparable efficiencies possibly without the anticompetitive (market power) effects of mergers. We empirically account for the endogenous formation of mergers and RJVs and provide evidence that at the semiconductor level, mergers and RJVs achieve dominant (net) efficiency effects. Our counterfactuals provide evidence that the efficiency gains caused by mergers would have been achieved by RJVs as well. Therefore, RJVs often represent viable alternatives to mergers from the consumer welfare point of view. At the more disaggregate level we find that the efficiency effects are larger in the microcomponents than in the memory market. This finding emphasizes the importance of market determinants (such as product differentiation and entry) having an impact on efficiency and market power effects.