Mixed oligopoly at free entry markets

We investigate the optimal behavior of a public firm in a mixed market involving private firms and one public firm. Existing works show that welfare-maximizing behavior by the public firm is suboptimal when the number of firms is given exogenously. We allow free entry of private firms and find that, in contrast to the case with the fixed number of firms, welfare-maximizing behavior by the public firm is always optimal in mixed markets. Furthermore, we find that mixed markets are better than pure markets involving no public firm if and only if the public firm earns nonnegative profits.