64 ECONOMIC ESSAYS IN HONOR OF JOHN BATES = 
~e — EE ——— 
and’s two magnitudes, S, and W.,, taken as our standards or 
artic, ene 
ach of these four calculations forms a chain. The first link 
n each chain,—S; or W, as the case may be,—is supposed to be 
iven. This first link may be assumed as any convenient figure. 
et us take S, equal to $600, and W, equal to unity. To coin b 
ord, we may call this latter unit a “wantab” (which may be 
egarded as an abbreviation either of “wantability” or of “want 
ab,” (i.e. a unit for keeping tab on the strength of a want). 
et us then pass from W, toward Wi, beginning with W,—=1 
antab, as the first step. The next step is to calculate the want- 
or-one-more pound of food per-annum of the family in Evenland 
y multiplying W, by Fs, the price per pound, giving W, F> or, 
since Wy=1 and F,—1) 1X1=1 wantab. - 
his multiplication is in accordance with the fundamental 
rinciple connecting want-for-one-more unit and price per unit. 
n its simplest application this principle tells us that (at the 
‘margin’ or limit of purchase, or of consumption) if, say, bread 
osts 12 cents a pound, the want-for-one-more pound of bread 
twelve times the want-for-one-more cent. 
he next magnitude is the want-for-one-more pound of food in 
ase 1. By hypothesis this is to be the same as in 2. That 
S WwW, F, (=1)=%W; Fi. 
Be his follows because, according to our hypothesi kno 
I 
that: 
(1) The want schedules (including that for food) in all three 
Cases (and so in Cases 1 and 2) are identical; 
(2) The food rations in these two Cases are the same in 
quantity and quality; 
(3) The want-for-one-more pound of food is assumed to be 
a function of this food ration, and of nothing else (and so is 
not affected by the fact that the housing accommodation differs 
in the two Cases). 
The next magnitude to be found, and the last in this particular 
chain, is Wy, the want-for-one-more dollar in Case 1. This we 
get, by dividing W; Fy, known to be unity, by Fi, the price of 
food in Oddland. This figure is supposed to be known from 
* For a mathematical discussion of this almost self-evident principle, 
the reader may consult any mathematical writer on value and price such 
as Jevons, Marshall, Edgeworth, Gossen, Mangoldt, Laundardt, Walras. 
Pareto, Bowley, or my own, Mathematical Investigations. n. 36.