42 
POLITICAL ECONOMY 
of elasticity in demand can be measured with 
reference to the elasticity which is termed 
“ unity.” Demand is said to have elastic 
unity when a fall in the price involves such 
increase of sales that the total amount paid 
for the aggregate of the thing sold remains 
the same. Beneath is represented a demand 
with an elasticity at first greater than unity, 
then equal to unity and finally less than 
unity. Let us suppose that the article 
referred to is some kind of soap. 
Price per lb. Total sal os in Total receipts in 
in pence. lbs. per month. pence per month. 
10 .. .. 30 .. ..300 
9 .. .. 40 .. .. 360 
8 .. .. 50 .. .. 400 
7 .. .. 60 .. ..420 
6 .. .. 70 .. ..420 
5 .. .. 84 .. .. 420 
4 .. .. 100 .. .. 400 
2 . . .. 150 .. .. 300 
1 .. .. 250 .. ..250 
demand is greater than 
prices lOd. and 7d., less 
than unity between the prices 5d. and Id., 
and equal to unity between the prices 7d. 
and 5d. 
The elasticity of 
unity between the 
One of the simplest generalisations in