Entry and mergers in oligopoly with firm-specific network effects

This paper investigates the effects of exogenous entry on market performance, and the profitability and welfare effects of horizontal mergers in symmetric Cournot oligopolies with firm-specific network effects. With strategic substitutes in the Cournot part of the model, per-firm output is declining in the number of firms, but industry output, price, per-firm profit, consumer surplus and social welfare may go either way in response to entry. We identify respective sufficient conditions for each possibility. The counter-intuitive conclusions tend to require strong network effects. We study the scope for profitability of mergers and the associated welfare effects. In a general analysis, we provide a sufficient condition on inverse demand for a merger to be profitable, which amounts to requiring strong network effects. Under the condition that leads to higher industry output with entry, mergers are always social welfare-enhancing.