Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-1454_5h26.pdf
Page Number: 45

Cite as:  585 U. S. ____ (2018) 

21 

BREYER, J., dissenting 

District  Court  followed  in  this  case,  by  considering  the 
effects of “[t]he two-sided nature of the . . . card industry”
throughout its analysis.  88 F. Supp. 3d, at 155.

Neither  the  majority  nor  the  academic  articles  it  cites
offer any explanation for why the features of a “two-sided 
transaction platform” justify always treating it as a single 
antitrust market, rather than accounting for its economic 
features  in  other  ways,  as  the  District  Court  did.  The 
article that the majority repeatedly quotes as saying that
“ ‘[i]n  two-sided  transaction  markets,  only  one  market
should  be  defined,’ ”  ante,  at  14–15  (quoting  Filistrucchi
302),  justifies  that  conclusion  only  for  purposes  of  as­
sessing the effects of a merger.  In such a case, the article 
explains, “[e]veryone would probably agree that a payment
card  company  such  as  American  Express  is  either  in  the 
relevant market on both sides or on neither side . . . .  The 
analysis of a merger between two payment card platforms 
should thus consider . . . both sides of the market.”  Id., at 
301.  In a merger case this makes sense, but is also mean­
ingless,  because,  whether  there  is  one  market  or  two,  a 
reviewing  court  will  consider  both  sides,  because  it  must
examine the effects of the merger in each affected market
and  submarket.  See  Brown  Shoe  Co.,  370  U. S.,  at  325. 
As  for  a  nonmerger  case,  the  article  offers  only  United 
States  v.  Grinnell  as  a  justification,  see  Filistrucchi  303,
and as I have already explained, supra, at 16–18, Grinnell 
does not support this proposition. 

E 
Put all of those substantial problems with the majority’s
reasoning  aside,  though.  Even  if  the  majority  were  right
to say that market definition was relevant, and even if the
majority were right to further say that the District Court
should  have  defined  the  market  in  this  case  to  include 
shopper-related  services  as  well  as  merchant-related 
services, that still would not justify the majority in affirm­