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POLITICAL ECONOMY 
price. It is extremely important to observe that 
this theory in its bearing on employed factors 
does not declare that each agent gets what it 
makes, but merely that each agent gets the 
difference that it makes to the total output 
of a productive group which is organized to 
work as a whole. Finally, to complete the 
theory we have the doctrine of rent which 
accounts for payments made on behalf of 
agents which enjoy differential advantages. 
It needs no specific intimation that in this 
theory it is marginal incidents that play the 
leading parts, just as it was marginal incidents 
which enabled us to comprehend fully the 
phenomena of price. Now, in relation to 
price, we observed that an incisive applica 
tion of the marginal method on the side 
of demand brought out a novel feature 
known as consumer’s surplus ; and it remains 
to investigate whether a similar feature may 
not be revealed on the side of supply. It may 
be said at once that a similar feature will be 
found to exist. It is called producer’s surplus. 
Broadly put consumer’s surplus stands for 
the difference between the value that a con 
sumer gets from a thing and the value that 
he gives for it when he purchases it. Then, to 
be strictly analogous, producer’s surplus 
should stand for the difference between the