the most good. When
he is nearly satiated with food, he needs other things more than he
does food stuffs. If he has secured so much of one product that any
additional amount that he may get by an hour's labor would be of less
use to him than what he could get of some other product by the same
amount of labor, it is important for him to change his occupation and
produce that thing of which an additional unit--which will perhaps be
the final unit of this more desirable article--has the higher degree
of usefulness.

_Final Utility and Labor Cost._--On the supposition that a small store
of roots and nuts were incapable of being replaced by any amount of
effort and that no other food were to be had, the utility of it would
be indefinitely great, since the man's life would depend on this one
increment of food alone. A man would value that life-sustaining good
for what it would do for him and without any reference to the amount
of work he had performed in order to get it, or to the amount he would
have to perform in order to get another store like it. On the
supposition that by labor the man could replace this essential supply,
the effective utility of it would be gauged by the sacrifice he would
have to make in order to replace it. The effective utility of any unit
of a good that an hour's labor will produce can never be more than
enough to offset the disutility of a marginal or final hour of labor;
and thus even a single unit of replaceable food stuff, even when it
stands alone and constitutes the whole supply, is valued according to
the cost of getting another one like it. A man will prize it according
to his dread of the sacrifice involved in getting the duplicate. If he
gets this by adding an hour of labor to his day's work, this fact is
an evidence that the importance of the original supply of the food is
measured and expressed by this personal cost of replacement; and as
any similar quantity in a large supply of food can be duplicated by
the same amount of labor, it appears that, by a standard based on
cost, the _effective_ utilities of all units are equal, that of each
one is measured by the "disutility" of an hour's labor and that of the
whole supply is this amount multiplied by the number of units that
this supply contains.[4]

[4] [Illustration]

Although we may use the terms _final utility_ and _effective
utility_ in a way that makes them nearly interchangeable, it
is clear that the qualities f