It will be noted however that the demand prices of each commodity, on which our estimates of its total utility and consumers, surplus are based, assume that other things remain equal, while its price rises to scarcity value: and when the total utilities of two commodities which contribute to the same purpose are calculated on this plan, we cannot say that the total utility of the two together is equal to the sum of the total utilities of each separately.(7*)4.The substance of our argument would not be affected if we took account of the fact that, the more a person spends on anything the less power he retains of purchasing more of it or of other things, and the greater is the value of money to him (in the technical language every fresh expenditure increases the marginal value of money to him).But though its substance would not be altered, its form would be made more intricate without any corresponding gain; for there are very few practical problems, in which the corrections to be made under this head would be of any importance.(8*)There are however some exceptions.For instance, as Sir R.
Giffen has pointed out, a rise in the price of bread makes so large a drain on the resources of the poorer labouring families and raises so much the marginal utility of money to them, that they are forced to curtail their consumption of meat and the more expensive farinaceous foods: and, bread being still the cheapest food which they can get and will take, they consume more, and not less of it.But such cases are rare; when they are met with, each must be treated on its own merits.
It has already been remarked that we cannot guess at all accurately how much of anything people would buy at prices very different from those which they are accustomed to pay for it: or in other words, what the demand prices for it would be for amounts very different from those which are commonly sold.Our list of demand prices is therefore highly conjectural except in the neighbourhood of the customary price; and the best estimates we can form of the whole amount of the utility of anything are liable to large error.But this difficulty is not important practically.For the chief applications of the doctrine of consumers' surplus are concerned with such changes in it as would accompany changes in the price of the commodity in question in the neighbourhood of the customary price: that is, they require us to use only that information with which we are fairly well supplied.These remarks apply with special force to necessaries.(9*)5.There remains another class of considerations which are apt to be overlooked in estimating the dependence of wellbeing upon material wealth.Not only does a person's happiness often depend more on his own physical, mental and moral health than on his external conditions: but even among these conditions many that are of chief importance for his real happiness are apt to be omitted from an inventory of his wealth.Some are free gifts of nature; and these might indeed be neglected without great harm if they were always the same for everybody; but in fact they vary much from place to place.More of them however are elements of collective wealth which are often omitted from the reckoning of individual wealth; but which become important when we compare different parts of the modern civilized world, and even more important when we compare our own age with earlier times.
Collective action for the purposes of securing common wellbeing, as for instance in lighting and watering the streets, will occupy us much towards the end of our inquiries.
Co-operative associations for the purchase of things for personal consumption have made more progress in England than elsewhere:
but those for purchasing the things wanted for trade purposes by farmers and others, have until lately been backward in England.
Both kinds are sometimes described as Consumers' associations;but they are really associations for economizing effort in certain branches of business, and belong to the subject of Production rather than Consumption.
6.When we speak of the dependence of wellbeing on material wealth, we refer to the flow or stream of wellbeing as measured by the flow or stream of incoming wealth an d the consequent power of using and consuming it.A person's stock of wealth yields by its usance and in other ways an income of happiness, among which of course are to be counted the pleasures of possession: but there is little direct connection between the aggregate amount of that stock and his aggregate happiness.And it is for that reason that we have throughout this and preceding chapters spoken of the rich, the middle classes and the poor as having respectively large, medium and small incomes - not possessions.(10*)In accordance with a suggestion made by Daniel Bernoulli, we may regard the satisfaction which a person derives from his income as commencing when he has enough to support life, and afterwards as increasing by equal amounts with every equal successive percentage that is added to his income; and vice versa for loss of income.(11*)But after a time new riches often lose a great part of their charms.Partly this is the result of familiarity; which makes people cease to derive much pleasure from accustomed comforts and luxuries, though they suffer greater pain from their loss.Partly it is due to the fact that with increased riches there often comes either the weariness of age, or at least an increase of nervous strain; and perhaps even habits of living that lower physical vitality, and diminish the capacity for pleasure.
