SUPPLY  AND  DEMAND

83

expenses  multiplied  by  its  output.  The  last
part  of  this  proposition  must  hold  because  the
employer’s  remuneration,  apart  from  payment ­
  for  his  capital,  is  represented  by  the
excess  of  his  aggregate  receipts  over  his  aggregate ­
  outgoings.  At  "a  position  of  perfect
equilibrium,  it  may  be  remarked  incidentally,
this  difference,  in  the  case  of  the  marginal
firm,  must  be  an  amount  just  sufficient  to  have
induced  the  employer  of  marginal  capacity  to
embark  on  production  in  the  industry.  If  it
were  more,  more  employers  would  be  attracted  ;
if  it  were  less  there  would  eventually  be  fewer
employers.  Super-marginal  employers,  owing
to  their  greater  ability,  may  be  getting  more
than  they  would  have  worked  for,  but  they
will  not  produce  more  than  they  do  because  it
would  not  pay  them,  whatever  they  are
earning,  to  manufacture  an  extra  pair  of  boots
for  sale  at  14s.  when  the  addition  to  their
aggregate  costs  would  exceed  14s.
In  order  that  no  link  may  be  missing  in
the  chain  of  reasoning,  the  above  exposition
may  be  supplemented  by  a  brief  survey  of
the  changes  which  occur  when  demand  rises.
Demand  having  risen,  more  than  14s.  a  pair
would  be  paid  for  boots,  were  only  12,000
pairs  obtainable,  and  our  six  firms  would  be
induced  to  extend  their  operations  if  it  were