the product of a single unit of labor is the
amount that is attributable to the productive fund only.

The area _ABDE_ represents this amount. The last unit of labor creates
the amount _DE_ and the number of units is represented by the amount
_AE_. All of them are now equally productive and what all create, as
apart from what capital creates, is the amount _ABDE_.

_Only the Final Part of this Mode of gathering a Working Force
practically resorted To._--The process of building up the working
force from a single unit is imaginary. In practical life we see the
process only in its final stage. _Entrepreneurs_ do continually have
to test the effect of making their working forces a little larger or a
little smaller, and in so doing they test the final productivity of
labor; and this is all that is necessary. Tracing the process of
building up the force of labor unit by unit reveals a law which is
important, namely, that of the diminishing productivity of single
units of labor as the number of units increases. If we crowd the world
full of people but do not proportionately multiply working appliances
of every kind, we shall make labor poorer.

_Why a Detachment of Laborers rather than One Man is treated as a Unit
of Labor._--In making up the force of workers we might have treated
each individual as a unit; but we have preferred to call a detachment
a unit in order that the symmetry of the force might be preserved.
Even though we were studying only a single mill it would have its
departments, and it would be desirable that, when we enlarge the force
of men, we should be able without difficulty to give to each part of
the mill its fair share of the new laborers. If it were a shoe
factory, we should need to add lasters, welters, sewers of uppers,
etc., in a certain proportionate way, in order that one part of the
mill might not get ahead of another and pile up unfinished products
faster than they could be taken and completed.

In the last analysis the law applies to the industry of all society.
The final unit in the case consists of shoemakers, cotton spinners,
builders, foundrymen, miners, cultivators, etc., and of men of all
subtrades included in the general callings. As the composite
detachments come into the field, they apportion themselves among all
the occupations that are represented, and that too in nicely adjusted
proportions. We shall see in due time how this adjustment of the
several shares of the social force of