Economical Election

In this and in every other case where satisfactions of different degrees of importance depend on command of a given quantity of goods, we are, above all, faced with the difficult question: which particular satisfaction is dependent on a particular portion of the quantity of goods in question?

The solution of this most important question of the theory of value follows from reflection upon human economy and the nature of value.

We have seen that the efforts of men are directed toward fully satisfying their needs, and where this is impossible, toward satisfying them as completely as possible. If a quantity of goods stands opposite needs of varying importance to men, they will first satisfy, or provide for, those needs whose satisfaction has the greatest importance to them. If there are any goods remaining, they will direct them to the satisfaction of needs that are next in degree of importance to those already satisfied. Any further remainder will be applied consecutively to the satisfaction of needs that come next in degree of importance.9

If a good can be used for the satisfaction of several different kinds of needs, and if, with respect to each kind of need, successive single acts of satisfaction each have diminishing importance according to the degree of completeness with which the need in question has already been satisfied, economizing men will first employ the quantities of the good that are available to them to secure those acts of satisfaction, without regard to the kind of need, which have the highest importance for them. They will employ any remaining quantities to secure satisfactions of concrete needs that are next in importance, and any further remainder to secure successively less important satisfactions. The end result of this procedure is that the most important of the satisfactions that cannot be achieved have the same importance for every kind of need, and hence that all needs are being satisfied up to an equal degree of importance of the separate acts of satisfaction.

We have been asking what value a given unit of a quantity of goods possessed by an economizing individual has for him. Our question can be more precisely stated with respect to the nature of value if it is stated in this form: which satisfaction would not be attained if the economizing individual did not have the given unit at his disposal-that is, if he were to have command of a total amount smaller by that one unit? The answer, which follows from the previous exposition of the nature of human economy, is that every economizing individual would in this case, with the quantity of goods yet remaining to him, by all means satisfy his more important needs and forgo satisfaction of the less important ones. Thus, of all the satisfactions previously obtained, only the one that has the smallest importance to him would now be  unattained.

Accordingly, in every concrete case, of all the satisfactions secured by means of the whole quantity of a good at the disposal of an economizing individual, only those that have the least importance to him are dependent on the availability of a given portion of the whole quantity. Hence the value to this person of any portion of the whole available quantity of the good is equal to the importance to him of the satisfactions of least importance among those assured by the whole quantity and achieved with an equal portion.10

Suppose that an individual needs 10 discrete units (or 10 measures) of a good for the full satisfaction of all his needs for that good, that these needs vary in importance from 10 to 1, but that he has only 7 units (or only 7 measures) of the good at his command. From what has been said about the nature of human  economy it is directly evident that this individual will satisfy only those of his needs for the good that range in importance from 10 to 4 with the quantity at his command (7 units), and that the other needs, ranging
in importance from 3 to 1, will remain unsatisfied. What is the value to the economizing individual in  question of one of his 7 units (or measures) in this case? According to what we have learned about the nature of the value of goods, this question is equivalent to the question: what is the importance of the satisfactions that would be unattained if the individual concerned were to have only 6 instead of 7 units (or measures) at his command. If some accident were to deprive him of one of his seven goods (or measures), it is clear that the person in question would use the remaining 6 units to satisfy the more important needs and would neglect the least important one. Hence the result of losing one good (or one measure) would be that only the least of all the satisfactions assured by the whole available quantity of seven units (i.e., the satisfaction whose importance was designated as 4) would be lost, while those satisfactions (or acts of satisfying needs) whose importance ranges from 10 to 5 would take place as before. In this case, therefore, only a satisfaction whose importance was designated by 4 will depend on command of a single unit (or measure), and as long as the individual in question continues to have command of 7 units (or  measures) of the good, the value of each unit (or measure) will be equal to the importance of this satisfaction. For it is only this satisfaction with an importance of 4 that depends on one unit (or measure) of the available quantity of the good. Other things being equal, if only 5 units (or measures) of the good were available to the economizing individual in question, it is evident that-as long as this economic situation persisted-each discrete unit or partial quantity of the good would have an importance to him expressed
numerically by the figure 6. If he had 3 units, each one would have an importance to him expressed  numerically by the figure 8. Finally, if he had but a single good, its importance would be equal to 10.

Taken From : PRINCIPLES OF ECONOMICS