so 
POLITICAL ECONOMY 
the marginal expense in the business, for it 
is the addition made to the total expense in 
the business when the output is increased by 
one pair of boots. Let the output of the 
business continue to increase by increments 
of one pair of boots each ; then there would 
be corresponding additions to total cost 
(called marginal costs or expenses as we have 
seen) say, 14s. lid., 14s. 10d., 14s. 8d., 
14s. 9d., and so on successively. 
If we watched such a gradual growth of a 
business or firm from an insignificant size it 
would be found that marginal costs would fall 
at first, for reasons already advanced. Now, 
can this fall in marginal expense go on in 
definitely ? The obvious and correct answer 
is that it cannot ordinarily. If it did, the 
chances are that by this time each industry 
would have become the monopoly of a 
single firm, which owed its position to the 
fact that, having once got a start, it was 
enabled to undersell its competitors until 
there were no competitors left to undersell. 
The fall in marginal cost cannot ordinarily 
continue without end, because the scope for 
further specialism and use of machinery 
afforded by further extensions of the business 
would tend to be neglected by the over-taxed 
brain of the ultimate head ; and any economy