s of labor performed at the end of several
working days when the sacrifice is greatest. Total value is
thus quantitatively equivalent to total _effective sacrifice
of replacement_, as well as to total effective utility. If,
by adding a brief period to the length of one working day, a
man can make good the loss of one unit of the goods, by
adding the same period to the length of a number of working
days, he can make good the loss of the total supply. For
simplicity we assume that the man's physical condition
remains unchanged, and that an extra hour of labor at the end
of any one day costs him as much as it would at the end of
any other.

_How Primitive Man measures the Productivity of Labor and
Capital._--There is a truth relating to producers' wealth that
resembles the truth that we have just stated with regard to consumers'
wealth. The more consumers' goods of one kind a man has, the less is
the value that any one of them has to him. The more producers' goods
of a given kind a man has, the less is the efficiency that any
particular one of them possesses as an aid to labor. The last bit of
bread serves the man himself in a less important way than does the
first, inasmuch as it gratifies a want that is less intense; and the
last implement of a given kind--the last hatchet or spade or
arrow--helps him less in his productive operations than did the first
one. On the one hand, we have the law of the diminishing utility of
successive units of consumers' goods, and on the other hand, we have a
parallel law of the diminishing productivity of successive increments
of producers' goods.

_The Necessity for measuring the Productive Powers of Capital Goods
even in Primitive Life._--Now, it is necessary for every producer,
though living in the simplest possible manner, to measure in some way
the efficiency of the last unit of each kind of productive instrument
that he uses. He has, let us say, a certain number of hatchets and of
arrows, and he can produce one hatchet with the same amount of labor
that would produce an arrow. Now, if a hatchet will do more good than
an arrow, he will direct his energies to the making of the hatchet. It
is important that any producer should bring the final units of the
different parts of his equipment to a certain uniformity of producing
power. He must not go on adding to the stock of implement No. 1 when
implement No. 2, which could be had by the same e