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;