InterchangeFeesandNeutralityinPaymentSystems.Theformalanaly-sisofinterchangefeeswasinitiatedbyBaxter(1983),followinganantitrustlawsuitagainsttheVisaassociation.11Hismaincontributionisaneutralityresultstat-ingthattheleveloftheinterchangefeeisirrelevanttoconsumerprices,providedthatboththeissuersandtheacquirersareperfectlycompetitive.Inamoregeneralanalysis,GansandKing(2003)showthatneutralityholdsregardlessofthelevelofcompetitionbetweenmerchantsandbetween nancialinstitutionsintheabsenceofthesocalledno-surchargerule(NSR).12TheiranalysisimpliesthattheinterchangefeeisgenerallyneutraliftheNSRislifted.Indeedinthiscase,cardusersfacethewholecostofusingacardandhencethereisnoexternality.

AssumingtheNSRtohold,RochetandTirole(2002)letanissuing nancialinstitutionhavemarketpower,theacquiringinstitutionsbeperfectlycompetitiveandmodelmerchantcompetitionalaHotelling.They ndthatthereexistsequi-libriawheremerchantsprefertonotacceptcardpayments—“merchantresistance”—andtheiracceptancepoliciesexhibitstrategiccomplementarity.TheinteractionoftheexternalitygeneratedbytheimpositionoftheNSRwithmerchants’behaviorimpliesthatthepro t-maximizinginterchangefeemaybehigherorlowerthanthewelfare-maximizingone;whenitishigher(lower),theremaybetoomany(few)cardtransactions,respectively.Theythengoontoanalyzethedeterminantsof“merchantresistance”.Inparticular,competitionbetweencardassociationstendstoincrease“merchantresistance”,becauseassociationsnowcompeteformerchantacceptancethroughthemerchantcharge(drivenbytheinterchangefee).However,liftingtheNSRmayincreaseordecreasewelfare.

ByrelaxingtheperfectcompetitionassumptioninBaxter(1983)andassumingimplicitlytheNSRtohold,Schmalensee(2002)attemptstocapturethedouble-sidedexternalityinthesemarketsandarguesthataninterchangefeeisnecessarytobalancecardholderandmerchantdemands.RochetandTirole(2002)andRoger(2002)highlightthecriticalroleoftheno-surchargerule.Indeed,thisruleturnsregular,one-sidedmarketswhereuserscompletelyinternalizetheirconsumptionoftheserviceintotrickiertwo-sidedmarkets,wheredemandfortheserviceononesidegeneratesanexternalityontheotherside.Thistwo-sidedness,whenappliedtothe

NationalBancardCorporation(NaBanco),aspecializedacquirer,suedVisainJune1979,claimingthatVisa’sinterchangefeearrangementsconstitutedaviolationoftheShermanAct.VisawonthebattlebothintheDistrictCourtandintheAppellateCourt.Thecaseendedin1986whentheSupremeCourtdeclinedtoreviewtheAppellateCourt’sdecision.SincethenVisacontinuedtousetheinterchangefeesystem.

12Theno-surchargerule(NSR)isacontractualagreementbetweenmerchantsandtheir(acquir-ing)bankstonotchargedi erentpricestocardusersandothercustomers.11