But in regard to demand and supply of particular commodities (not general demand and supply), the increase of the demand [pg 256] is not necessarily followed by an increased supply, or vice versa. Out of the total production (which constitutes general demand) a varying amount, sometimes more, sometimes less, may be directed by the desires of men to the purchase of some given thing. This should be borne in mind, in connection with the future discussion of over-production. The identity of general demand with general supply shows there can be no general over-production: but so long as there exists the possibility that the demand for a particular commodity may diminish without a corresponding effect being thereby produced on the supply of that commodity, by a necessary connection, we see that there may be over-production of particular commodities; that is, a production in excess of the demand.
The proper mathematical analogy [between demand and supply] is that of an equation. If unequal at any moment, competition equalizes them, and the manner in which this is done is by an adjustment of the value. If the demand increases, the value rises; if the demand diminishes, the value falls; again, if the supply falls off, the value rises; and falls, if the supply is increased. The rise or the fall continues until the demand and supply are again equal to one another: and the value which a commodity will bring in any market is no other than the value which, in that market, gives a demand just sufficient to carry off the existing or expected supply.
Mr. Cairnes[209] finally defined market value as the price “which is sufficient, and no more than sufficient, to carry the existing supply over, with such a surplus as circumstances may render advisable, to meet the new supplies forthcoming,” which is nothing more than a paraphrase of the words “existing or expected supply” just used by Mr. Mill. It seems unnecessary, therefore, that Mr. Cairnes should have added: “According to Mr. Mill, the actual market price is the price which equalizes supply and demand in a given market; as I view the case, the ‘proper market price’ is the price which equalizes supply and demand, not as existing in the particular market, but in the larger sense which I have assigned to the terms. To this price the actual market price will, according to my view, approximate, in proportion to the intelligence and knowledge of the dealers.”
Adam Smith, who introduced the expression “effectual demand,” employed it to denote the demand of those who are willing and able to give for the commodity what he calls its natural price—that is, the price which will enable it to be permanently produced and brought to market.[210]
This, then, is the Law of Value, with respect to all commodities not susceptible of being multiplied at pleasure.
§ 4. Miscellaneous Cases falling under this Law.
There are but few commodities which are naturally and necessarily limited in supply. But any commodity whatever may be artificially so. The monopolist can fix the value as high as he pleases, short of what the consumer either could not or would not pay; but he can only do so by limiting the supply. Monopoly value, therefore, does not depend on any peculiar principle, but is a mere variety of the ordinary case of demand and supply.
Again, though there are few commodities which are at all times and forever unsusceptible of increase of supply, any commodity whatever may be temporarily so; and with some commodities this is habitually the case. Agricultural produce, for example, can not be increased in quantity before the next harvest; the quantity of corn already existing in the world is all that can be had for sometimes a year to come. During that interval, corn is practically assimilated to things of which the quantity can not be increased. In the case of most commodities, it requires a certain time to increase their quantity; and if the demand increases, then, until a corresponding supply can be brought forward, that is, until the supply can accommodate itself to the demand, the value will so rise as to accommodate the demand to the supply.
There is another case the exact converse of this. There are some articles of which the supply may be indefinitely increased, but can not be rapidly diminished. There are things so durable that the quantity in existence is at all times very great in comparison with the annual produce. Gold [pg 258] and the more durable metals are things of this sort, and also houses. The supply of such things might be at once diminished by destroying them; but to do this could only be the interest of the possessor if he had a monopoly of the article, and could repay himself for the destruction of a part by the increased value of the remainder. The value, therefore, of such things may continue for a long time so low, either from excess of supply or falling off in the demand, as to put a complete stop to further production; the diminution of supply by wearing out being so slow a process that a long time is requisite, even under a total suspension of production, to restore the original value. During that interval the value will be regulated solely by supply and demand, and will rise very gradually as the existing stock wears out, until there is again a remunerating value, and production resumes its course.