Public monopoly versus mixed oligopoly: product differentiation and social efficiency

In this paper, we consider a mixed oligopoly market in which a public firm and private firms compete, in particular, in which private entrants are allowed to enter a monopoly market by a public incumbent who maximizes social welfare. It has been widely believed that the public firm has advantage over private firms because the former who maximizes social welfare can charge a lower price than the latter who maximizes its own profit. However, in a Hotelling model of product differentiation, we obtain the results that both the public firm and private firms charge the same price in equilibrium, and more importantly, that the equilibrium prices may rise as a result of competition, thereby lowering the consumer surplus, if the transportation cost is high enough. We also show that if a private firm enters the market by choosing its own degree of differentiation, it will prefer neither maximum differentiation nor minimum differentiation in the case that the public incumbent is myopic in the sense that it cannot anticipate entry as well as in the case that it is far-sighted enough to anticipate entry. This draws an important policy implication in the market of Korean housing guarantee services.