The Welfare Effects of Regulating the Number of Market Segments

We consider a model in which a profit-maximizing organization called the monopolist faces N _ 2 different (micro) market segments while the number k of market segments is chosen the regulator, where k is an integer between 1 and N. Unless k = 1 or k = N, the monopolist's profit maximization is a mixed-integer programming problem, the solution of which is called the optimal profit policy. When demands are linear, we show that it is always worthwhile to regulate the number of market segments since the value of k that maximizes the social welfare under the optimal profit policy is never greater than a critical threshold _k. This result allows us to disentangle the good aspect of price discrimination, the so-called output effect, from the bad one, that we call the pure profit effect. Further results are provided for the specific case of parallel demands. Non-linear demands are also briefly considered.