THE PROBLEM OF WAGES 119

product due to a loss of a workman, or the gain due to the
addition of a workman, represents that workman's effective
product. But this can only be maintained if the change of
numbers does not involve leaving some machinery, or other
productive appliances, wholly or partially idle, that is, if the
removal of a workman simply removes his own contribution
to the product, and not, in addition, that of a machine, or
some part of that of other workmen. In conceiving of a
man’s net product, we must, therefore, either conceive of a
case where no readjustment, of appliances to numbers using
them, is needed when one additional man is added to, or
subtracted from, a working group, or else we must make
comparison between two cases, the one where the available
capital is given the forms needed for setting a larger number
of men at work, the other where the same amount of capital
is represented by appliances for a smaller number. When
the larger and smaller numbers differ by unity, the difference
in the product of the two groups is due, not to a difference
in any other element, but purely to the difference of a workman
 more or less, and we may, therefore, reasonably call
the difference the net product of that man’s labour. If we
may assume a knowledge of the interest on capital, the
conception may be made simpler. We have merely to
observe the difference in product due to the removal of
one workman, to determine further the capital rendered
idle by his removal, and, after assigning, from the total
decrease of product, so much to capital as will account for
the interest and depreciation on the capital thrown idle,
attribute the remainder to the workman.
In the preceding statement, the reference has been to
capital and labour alone. If there be other productive
agents to be taken into account, such as land or managing
services, the problem is made more complex, but is not
essentially altered in nature, or in method of treatment.
Having formed a conception of what we may regard as
a man’s contribution to production, his net product, we may
proceed to consider how it is related to his worth to his
employer, if he be hired. First let us suppose that his place
can be taken by any one of his fellow-workmen. Then it