sting itself on
man, benefits him; but during the period in which it is being prepared
for use, when it is receiving utilities at the hands of successive
producers, it has an opposite relation to the men who handle it. In
making the material useful a man confines and tires himself. He is
willing to do it if the reward that he expects will more than pay for
the sacrifice, but not otherwise. Moreover, this sacrifice itself has
to be estimated specifically in a way that is akin to the method of
measuring utilities which determines the values of goods. It is
necessary for a man to gauge the sacrifice which is entailed on him,
not by his labor as a whole, but by a specific part of it. He finds
himself in the evening feeling the fatigue and the sense of
confinement which the day of labor has imposed and asks himself how
much it would burden him to work a little longer. If what he can get
by this means pays for the extra sacrifice involved in thus getting
it, he will work for the few minutes, but otherwise he will not. His
objection to a few minutes of additional work measures what we may
call the specific disutility of labor; and men, whether they be
primitive or civilized, are forever making such measurements. They
consider how much it will cost them to add slightly to the length of
their working day or how much it will benefit them to shorten it. In
this way they measure the _specific disutility_ of labor rather than
the _total disutility_ of it, since they do not gauge the relief that
it would afford to cease working altogether.

_The Increasing Cost of Successive Periods of Labor._--It is easy to
work when one is not tired, and the first hour or two of labor may
even afford a pleasure that largely offsets the burden that it
entails; but it is hard to work when one is tired and painfully
conscious of the confinement of the shop. Adding anything to the
length of a working day imposes on a man the necessity of working at
the time when the burden is greatest; and shortening his day, for a
like reason, relieves him of some of his most costly toil.

_The Natural Length of the Working Day._--Any laborer, as his work
goes on, hour after hour, is certain to reach a point at which it is
unprofitable to go farther. However greatly he may need more goods, he
will not need them as much as he needs rest and change. It may be that
he has worked twelve hours, and that, by working longer, he can
improve his wardrobe, his food, or his fu