30

ECONOMIC PRINCIPLES

is ordinarily used, may be of either of two entirely distinct
 varieties. A fall of the price enables some demands
to become effective, which had not been so previous to the
fall, and leads to a larger quantity being called for; a rise
of price destroys the effectiveness of some part of the
demand, prevents those desires for the commodity, which are
keen enough to lead to its purchase at the old price, but not
sufficiently keen to outweigh the raised price, from attaining
satisfaction, thus diminishing the amount demanded. The
general appreciation of the services which the commodity
can render may, meanwhile, remain unchanged; that is to
say, the state of demand may be really unaltered while the
amount demanded responds to changes of price quotations.
Price-change, in fact, leads to extension or restriction of the
amount demanded, or, as is commonly said, of the demand,
though this phraseology does not really describe the true
nature of what is occurring.
Real changes of demand occur when the consumers of
a commodity, regarded as a group, experience a change in
their appreciation of the serviceability of the commodity.
[f this change be an increase, any specified price will evoke
a demand for a larger quantity than before the change,
while a higher price will be able to be exacted without
decreasing the amount demanded. Should the change be
of the opposite description, namely a decreased appreciation
of the commodity, any particular price will not call forth a
demand for so much as before of the goods, and, for any
specified amount to be disposed of, a lower price than before
the change will need to be fixed to ensure that the whole of
that amount will be demanded.
The first-named class of change merely deals with how
large a portion of the would-be consumers may become
actual consumers, the latter kind of change implies that the
consuming group has undergone a change of constitution, or
that a change in its tastes or habits has taken place. In the
former case there is not assumed to be any change in the
marginal utility of any given amount of supply, though a
change in the amount of the supply is contemplated; in the
latter case there is contemplated a change in the marginal