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Page Number: 40.0

16 

OHIO v. AMERICAN EXPRESS CO. 

BREYER, J., dissenting 

switches inserted into auto bodies and tires used for cars. 
I  have  already  explained  that,  ordinarily,  antitrust  law 
will not group the two nonsubstitutable products together
for step 1 purposes.  Supra, at 10–11. 

Neither  should  it  normally  matter  whether  a  company
sells  related,  or  complementary,  products,  i.e.,  products
which must both be purchased to have any function, such
as  ignition  switches  and  tires,  or  cameras  and  film.    It  is 
well established that an antitrust court in such cases looks 
at  the  product  where  the  attacked  restraint  has  an  anti­
competitive  effect.  Supra,  at  9;  see  Eastman  Kodak,  504 
U. S.,  at  463.  The  court  does  not  combine  the  customers 
for  the  separate,  nonsubstitutable  goods  and  see  if  “over­
all”  the  restraint  has  a  negative  effect.    See  ibid.;  2B 
Areeda  &  Hovenkamp  ¶565a.    That  is  because,  as  I  have 
explained,  the  complementary  relationship  between  the 
products is irrelevant to the purposes of market-definition. 
See supra, at 10–11. 

The majority disputes my characterization of merchant-
related  and  shopper-related  services  as  “complements.”
See  ante,  at  14,  n. 8.    The  majority  relies  on an  academic
article which devotes one sentence to the question, saying 
that  “a  two-sided  market  [is]  different  from  markets  for 
complementary  products  [e.g.,  tires  and  gas],  in  which
both  products  are  bought  by  the  same  buyers,  who,  in
their  buying  decisions,  can  therefore  be  expected  to  take 
into  account  both  prices.”  Filistrucchi,  Geradin,  Van 
Damme,  &  Affeldt,  Market  Definition  in  Two-Sided  Mar­
kets:  Theory  and  Practice,  10  J.  Competition  L.  &  Econ. 
293,  297  (2014)  (Filistrucchi). 
I  agree  that  two-sided
platforms—at  least  as  some  academics  define  them,  but 
see  infra,  at  19–20—may  be  distinct  from  some  types  of 
complements  in  the  respect  the  majority  mentions  (even
though  the  services  resemble  complements  because  they
must  be  used  together  for  either  to  have  value).  But  the 
distinction  the  majority  mentions  has  nothing  to  do  with