VII Simple Monopoly and Maximum Prices

§ 23. If the State, seeking to protect consumers against a monopoly, fixes a maximum price at the level proper to free competition, it is obvious that, under decreasing or constant supply price, the monopolist will gain by increasing his output up to the amount that would have been produced under free competition. If, however, conditions of increasing supply price prevail, the amount which it will pay the monopolist to produce, namely, the amount which will maximise output multiplied by the excess of the regulated price of sale over the supply price, is necessarily less than the competitive output. It may be either greater or less than the output that would result under unregulated monopoly. If the curves of demand and supply are both straight lines, it will be exactly equal to this amount. This is readily seen by inspection of a suitably drawn diagram.

§ 24. If, under conditions of increasing supply price, the State fixes a maximum price, less than the monopoly price but greater than the competitive price, it is probable in general that the output will be intermediate between the competitive output and the output proper to unregulated monopoly. If the curves of demand and supply are both straight lines, this result is certain. Construct a diagram (Fig. 9), such that PM represents the competitive price, and OM the competitive output; while QN represents the monopoly price, and ON the monopoly output. Let the State controlled price, measured by OV, be greater than the competitive price, but less than the monopoly price. Through V draw a horizontal line VBT cutting DD1 in B and SS1 in T. It is easily shown that the monopoly output ON is one-half of the competitive output OM, and that the output, which it will pay the monopolist to produce when the price is fixed at OV, will be measured by one-half of the line VT, drawn horizontally through V to cut SS1 in T, or by the line VB, according as the one or the other of these lengths is smaller. But, since OV is greater than PM, it is obvious that VT is greater than OM. Consequently one-half of VT is greater than one-half of OM. This proves that the output at the controlled price is greater than the monopoly output; and, since VB must be less than RP, it is necessarily less than the competitive output. That is, it lies somewhere between the two.

§ 25. An extension of the foregoing argument shows that, in the conditions contemplated, when the demand and supply curves are straight lines, the level of controlled price, which will make the output larger than any other level would do, will be that which causes the intersection point of VT and DD1, namely, the point B, to be identical with the middle point of VT, namely, the point H. If the angle SDP be and the angle DSP be , this output can be shown to be equal to the output proper to simple competition multiplied by the fraction