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12 

OHIO v. AMERICAN EXPRESS CO. 

Opinion of the Court 

563,  571  (1966).  But  courts  should  “combin[e]”  different 
products  or  services  into  “a  single  market”  when  “that
combination reflects commercial realities.”  Id., at 572; see 
also Brown Shoe Co. v. United States, 370 U. S. 294, 336– 
337 (1962) (pointing out that “the definition of the relevant 
market”  must  “ ‘correspond  to  the  commercial  realities’  of
the industry”).

As  explained,  credit-card  networks  are  two-sided  plat-
forms.  Due  to  indirect  network  effects,  two-sided  plat-
forms  cannot  raise  prices  on  one  side  without  risking  a
feedback  loop  of  declining  demand.  See  Evans  &  Schma-
lensee 674–675; Evans & Noel 680–681.  And the fact that 
two-sided  platforms  charge  one  side  a  price  that  is  below 
or above cost reflects differences in the two sides’ demand 
elasticity,  not  market  power  or  anticompetitive  pricing. 
See Klein 574, 595, 598, 626.  Price increases on one side 
of  the  platform  likewise  do  not  suggest  anticompetitive 
effects without some evidence that they have increased the
overall cost of the platform’s services.  See id., at 575, 594, 
626.  Thus,  courts  must  include  both  sides  of  the  plat-
form—merchants  and  cardholders—when  defining  the
credit-card market. 

To  be  sure,  it  is  not  always  necessary  to  consider  both 
sides of a two-sided platform.  A market should be treated 
as one sided when the impacts of indirect network effects
and  relative  pricing  in  that  market  are  minor.    See  Fil-
istrucchi  321–322.  Newspapers  that  sell  advertisements,
for  example,  arguably  operate  a  two-sided  platform  be-
cause  the  value  of  an  advertisement  increases  as  more 
people  read  the  newspaper.    Id.,  at  297,  315;  Klein  579. 
But  in  the  newspaper-advertisement  market,  the  indirect
networks  effects  operate  in  only  one  direction;  newspaper 
readers  are  largely  indifferent  to  the  amount  of  advertis-
ing that a newspaper contains.  See Filistrucchi 321, 323, 
and  n. 99;  Klein  583.    Because  of  these  weak  indirect 
network  effects,  the  market  for  newspaper  advertising