tion, and would be diminished if it fell below that ratio. But we must not therefore suppose it to be necessary that the supply should actually be either diminished or increased. Suppose that the cost of production of a thing is cheapened by some mechanical invention, or increased by a tax. The value of the thing would in a little time, if not immediately, fall in the one case, and rise in the other; and it would do so, because if it did not, the supply would in the one case be increased, until the price fell, in the other diminished, until it rose. For this reason, and from the erroneous notion that value depends on the proportion between the demand and the supply, many persons suppose that this proportion must be altered whenever there is any change in the value of the commodity; that the value cannot fall through a diminution of the cost of production, unless the supply is permanently increased; nor rise, unless the supply is permanently diminished. But this is not the fact: there is no need that there should be any actual alteration of supply; and when there is, the alteration, if permanent, is not the cause, but the consequence of the alteration in value. If, indeed, the supply could not be increased, no diminution in the cost of production would lower the value: but there is by no means any necessity that it should. The mere possibility often suffices; the dealers are aware of what would happen, and their mutual competition makes them anticipate the result by lowering the price. Whether there will be a greater permanent supply of the commodity after its production has been cheapened, depends on quite another question, namely, on whether a greater quantity is wanted at the reduced value. Most commonly a greater quantity is wanted, but not necessarily. "A man," says Mr. De Quincey,[1] "buys an article of instant applicability to his own purposes the more readily and the more largely as it happens to be cheaper. Silk handkerchiefs having fallen to half-price, he will buy, perhaps, in three-
- ↑ Logic of Political Economy, pp. 230-1.
