A STATISTICAL METHOD FOR MEASURING ‘MARGINAL UTILITY” 177
Nor does it seem likely that this want-for-one-more food unit
is dependent, in any important degree, on circumstances outside
the budget such as the character of the neighbors’ rations. As to
housing, on the other hand, the want-for-one-more unit will probably
 be appreciably affected by one’s neighbors’ standards. The
only way to eliminate this influence is to assume that the same
general social standards apply in Oddland as in Evenland. Probably,
 in actual practice, the chief difficulty in the way of accurate
statistical measurement will consist in getting cases differing in
income without differing greatly in the influence of social environment
 on the problem. As I see it, this is the only difficulty of
importance.
With this assumed, however, I cannot see any reason to doubt
the substantial truth of the proposition that, when the adjustment
 of housing accommodation to prices is effective in both
countries, the desire for one more housing unit is the same in
Cases 3 and 2.

Equation (2) Interpreted
We now ask anew, in what sense does the equation, W; F;—
Wy F,, mean that the family wants one more unit of the ration in
Case 1 exactly as intensely as the 2nd family wants one more
unit added to the same, or equivalent, ration in Case 2? Putting
this equation in the form ol = 7 and remembering that the W's
2 1
are per dollar, we see it means that our families’ wants-for-onemore
 dollar’s worth of the ration common to Cases 1 and 2 are
inversely as the price indexes in the two countries. Or again, by
using the reciprocal of this price index as an index of the
purchasing power of the dollar, and so putting the equation in
the form:

Wy _ UF;
Wa . 1/F,

he BLE

we may say that the want-for-one-more dollar, or for one more
dollar’s worth of the food ration, varies directly with the purchasing
 power (in terms of food) of the dollar. In our imaginary
calculations the common food ration of Cases 1 and 2 costs $400
in Oddland and $300 in Evenland, the price index being, in the
two Cases, as 4 to 3, or the purchasing power of the dollar as