182 ECONOMIC ESSAYS IN HONOR OF JOHN BATES CLARK
(e.g., Case 1) is worth the same subjectively in every direction, so
that we need, in each Case, only one designation, such as W,, for
its marginal want for a dollar, that is its want-for-one-more
dollar. Thus W, indicates the want-for-one-more dollar’s worth
of food, as well as for one more dollar’s worth of housing or
for one more dollar’s worth of anything else.
(b) Comparability. Wants of different groups of individuals
are assumed to be practically comparable. The behavior of
the average family under varying circumstances, as exemplified
in its budget and published in statistical tables according to
income, size of family, character of workmen, etc. is assumed
to register, and be adjusted to, the average intensities of the
wants of the average families recorded in those budget tables.
Thus we are permitted to compare Wy and W» for instance, in
the same equation, although they relate to two different groups
of people, one an average of many families in Oddland, and
the other an average of many families in Evenland.
(¢) Dependence of each want exclusively on the provision
for that want. Having thus acquired the right (from assump-
tion a) to employ a single uniform Wi and a single uniform
IW, instead of a multitude of unequal magnitudes, one for each use
of money, and (from assumption b) to compare said W; and
Ws, as applying to different people, we next assume that equal
increments added to equal rations of food are equally wanted
by families of equal size and character. This implies that the
want for a given small increment, or improvement in quantity
and quality, of a given ration (say of the common ration of
Cases 1 and 2) depends exclusively on that ration. Thus, it
will be the same for an average family of a given size and
sharacter in Oddland as it is for an average family of the same
size and character in Evenland, the income of these two average
families being different and only so related as to have led them
‘0 choose substantially the same ration.
It follows, since these equal increments of this ration are
equally desirable, that one more dollar’s worth of each ration
will be desired in exact proportion to the amount which the
dollar will purchase in the two markets. In other words
Ww, _ VF:
Wa 1/7;