In other words, he derives this 45s.worth of surplus enjoyment from his conjuncture, from the adaptation of the environment to his wants in the particular matter of tea.If that adaptation ceased, and tea could not be had at any price, he would have incurred a loss of satisfaction at least equal to that which he could have got by spending 45s.more on extra supplies of things that were worth to him only just what he paid for them.(3*)3.In the same way if we were to neglect for the moment the fact that the same sum of money represents different amounts of pleasure to different people, we might measure the surplus satisfaction which the sale of tea affords, say, in the London market, by the aggregate of the sums by which the prices shown in a complete list of demand prices for tea exceeds its selling price.(4*)This analysis, with its new names and elaborate machinery, appears at first sight laboured and unreal.On closer study it will be found to introduce no new difficulties and to make no new assumptions; but only to bring to light difficulties and assumptions that are latent in the common language of the market-place.For in this, as in other cases, the apparent simplicity of popular phrases veils a real complexity, and it is the duty of science to bring out that latent complexity; to face it; and to reduce it as far as possible: so that in later stages we may handle firmly difficulties that could not be grasped with a good grip by the vague thought and language of ordinary life.
It is a common saying in ordinary life that the real worth of things to a man is not gauged by the price he pays for them:
that, though he spends for instance much more on tea than on salt, yet salt is of greater real worth to him; and that this would be clearly seen if he were entirely deprived of it.This line of argument is but thrown into precise technical form when it is said that we cannot trust the marginal utility of a commodity to indicate its total utility.If some shipwrecked men, expecting to wait a year before they were rescued, had a few pounds of tea and the same number of pounds of salt to divide between them, the salt would be the more highly prized; because the marginal utility of an ounce of salt, when a person expects to get only a few of them in the year is greater than that of tea under like circumstances.But, under ordinary circumstances, the price of salt being low, every one buys so much of it that an additional pound would bring him little additional satisfaction:
the total utility of salt to him is very great indeed, and yet its marginal utility is low.On the other hand, since tea is costly, most people use less of it and let the water stay on it rather longer than they would, if it could be got at nearly as low a price as salt can.Their desire for it is far from being satiated: its marginal utility remains high, and they may be willing to pay as much for an additional ounce of it as they would for an additional pound of salt.The common saying of ordinary life with which we began suggests all this: but not in an exact and definite form, such as is needed for a statement which will often be applied in later work.The use of technical terms at starting adds nothing to knowledge: but it puts familiar knowledge in a firm compact shape, ready to serve as the basis for further study.(5*)Or the real worth of a thing might be discussed with:
reference not to a single person but to people in general; and thus it would naturally be assumed that a shilling's worth of gratification to one Englishman might be taken as equivalent with a shilling's worth to another, " to start with," and " until cause to the contrary were shown." But everyone would know that this was a reasonable course only on the supposition that the consumers of tea and those of salt belonged to the same classes of people; and included people of every variety of temperament.(6*)This involves the consideration that a pound's worth of satisfaction to an ordinary poor man is a much greater thing than a pound's worth of satisfaction to an ordinary rich man: and if instead of comparing tea and salt, which are both used largely by all classes, we compared either of them with champagne or pineapples, the correction to be made on this account would be more than important: it would change the whole character of the estimate.In earlier generations many statesmen, and even some economists, neglected to make adequate allowance for considerations of this class, especially when constructing schemes of taxation; and their words or deeds seemed to imply a want of sympathy with the sufferings of the poor; though more often they were due simply to want of thought.
On the whole however it happens that by far the greater number of the events with which economics deals, affect in about equal proportions all the different classes of society; so that if the money measures of the happiness caused by two events are equal, there is not in general any very great difference between the amounts of the happiness in the two cases.And it is on account of this fact that the exact measurement of the consumers'
surplus in a market has already much theoretical interest, and may become of high practical importance.
