SUPPLY AND VALUE 59

their current expenses, sacrificing income from their fixed plant
as they would sacrifice its value if forced to realise on it.
During the process of readjustment, then, the expenses
directly incurred in producing a commodity, its prime cost,
form a lower limit to value, but the total cost of production
will not be restored as a measure of value until production
is again held in check by the need of incurring those total
costs as a condition of maintaining the supply. Even the
prime cost may not be a lower limit to the amount which
may be accepted for stocks which, produced by ruined firms,
there is no intention of replacing, and in regard to which,
therefore, their costs of production, even in the narrow sense
of prime costs, have no influence on their supply. They
cannot be conceived of as forming part of a regular stream
of supply produced in view of an assured demand.
With rising demand, the more permanent parts of the
productive equipment will need to be strained beyond their
wont, and the prime costs of an increase of supply may well
be in excess of the prime costs for the supply for which that
equipment is adapted. If the total cost of production do
not greatly differ from the prime cost, the condition of
obtaining an enlarged supply is submission to a valuation
for the whole supply corresponding to the additional expensiveness
 of increasing that supply. But if prime costs
are a good deal less than total costs, the increase of production,
 yielding, as a result of the rising demand, a value
greater than the same supply would have secured without
that rise, affords a greater surplus of value over prime costs
than before. The productive equipment yields an increased
revenue, and this serves as a stimulus to its enlargement, if
the increase of demand be likely to be permanent. So long
as the cost of providing an enlarged equipment for production
 is less than would be reasonably remunerated by the
revenue anticipated from it, when provided, the expansion of
supply will be stimulated, and the competition of rival
producers will induce a provision of such means of
production up to the point where the total cost of production
of the goods for which they are used corresponds to their
value when produced