This paper considers the efficiency of a contestable natural monopoly if consumers are heterogeneous and the monopolist can differentiate prices imperfectly. With restricted entry, the standard result in this case is that the monopoly offers a menu of price-quantity combinations which leads to...

We consider rules (strategies, commitments, contracts, or computer programs) that make behavior contingent on an opponent’s rule. The set of perfectly observable rules is not well defined. Previous contributions avoid this problem by restricting the rules deemed admissible. We instead limit...