Next to a necessary in this respect will come what is termed a "conventional necessary," something which by custom has been firmly implanted as an integral portion of the standard of comfort. This differs, of course, in different classes of a community. Boots may now be regarded as a "conventional necessary" of almost all grades of English society, and a monopolist could probably raise the price of boots considerably without greatly diminishing the consumption. Half a century ago, however, when boots were not firmly established as part of the standard of comfort of the great mass of the working classes, the power of a monopolist to raise prices would have been far smaller.
As we descend in the urgency of wants supplied we find that the comforts and luxuries form a part of the standard of life of a smaller and smaller number of persons, and satisfying intrinsically weaker needs, are more liable to be affected by a rise of price.
(_b_) Closely related to this consideration, and working in with it at every point, is the question of the possibility of substituting another commodity for the one monopolised. This everywhere tempers the urgency of the need attaching to a commodity. There are few, if any, even among the commodities on which we habitually rely for food, shelter, clothing, which we could not and would not dispense with if prices rose very high. The incessant competition which is going on between different commodities which claim to satisfy some particular class of need cannot be got rid of by the monopoly of one of them. This is probably the chief explanation of the low prices of the Standard Oil. As an illuminant, oil is competing with gas, candles, electricity, and unless the monopoly were extended laterally so as to include these and any other possible illuminants, the Trust's prices cannot be determined merely by the pressure of the need for artificial light. Though to a modern society artificial light is probably even more important than sugar, a Sugar Trust may have a stronger monopoly and be able to raise prices higher than an Oil Trust, because the substitutes for sugar, such as molasses and beetroot, are less effective competitors than gas, candles, and electricity with oil.