不完全市场下的消费者剩余：在储蓄和小额信贷中的应用（英）

PublicDisclosureAuthorized PublicDisclosureAuthorized PolicyResearchWorkingPaper10481 ConsumerSurpluswithIncompleteMarkets ApplicationstoSavingsandMicrofinance JohnAshtonLoeser DevelopmentEconomics DevelopmentImpactEvaluationGroupJune2023 PolicyResearchWorkingPaper10481 Abstract Thehouseholdwelfaregainsfromfinancialinclusionareempiricallyelusive.Thispaperestablishesthathouseholdwelfaregainsfromafinancialtechnologyareequaltotheareaunderdynamicallycompensateddemandinahouse-holdmodelwithincompletefinancialmarkets,andgeneraltechnology,preferences,andchoicesets.Thispaperthen estimatescompensateddemandforfinancialtechnologiesleveragingthreerandomizedcontroltrialsthatintroduceexperimentalvariationininterestrates.Welfaregainsperdollarlentorsavedaresmallascompensateddemandelasticitiesarelarge,butstillcorrespondtolargeaggregatewelfaregainsfromfinancialinclusion. ThispaperisaproductoftheDevelopmentImpactEvaluationGroup,DevelopmentEconomics.ItispartofalargereffortbytheWorldBanktoprovideopenaccesstoitsresearchandmakeacontributiontodevelopmentpolicydiscussionsaroundtheworld.PolicyResearchWorkingPapersarealsopostedontheWebathttp://www.worldbank.org/prwp.Theauthormaybecontactedatjloeser@worldbank.org. ThePolicyResearchWorkingPaperSeriesdisseminatesthefindingsofworkinprogresstoencouragetheexchangeofideasaboutdevelopmentissues.Anobjectiveoftheseriesistogetthefindingsoutquickly,evenifthepresentationsarelessthanfullypolished.Thepaperscarrythenamesoftheauthorsandshouldbecitedaccordingly.Thefindings,interpretations,andconclusionsexpressedinthispaperareentirelythoseoftheauthors.TheydonotnecessarilyrepresenttheviewsoftheInternationalBankforReconstructionandDevelopment/WorldBankanditsaffiliatedorganizations,orthoseoftheExecutiveDirectorsoftheWorldBankorthegovernmentstheyrepresent. ProducedbytheResearchSupportTeam ConsumerSurpluswithIncompleteMarkets:ApplicationstoSavingsandMicrofinance∗ JohnLoeser† JELClassificationCodes:D11,D14,G51,O1,O12,O16 Keywords:Consumersurplus,Incompletefinancialmarkets,Financialinclusion ∗jloeser@worldbank.org.ThisresearchbenefitedfromsuggestionsandcommentsfromDanielAgness, KatyBergstrom,AlfredoBurlando,KieranByrne,AlaindeJanvry,EmmaFrankham,XavierGine,SeanHiggins,DahyeonJeong,ErinKelley,CynthiaKinnan,FlorenceKondylis,GregLane,AriannaLegovini,JeremyMagruder,AprajitMahajan,DavidMcKenzie,ElisabethSadoulet,HeeKwonSeo,UrsulaWiriad-inata,BrianWright,andseminaraudiencesatNEUDC,UCBerkeley,WEFIDEV,andtheWorldBank.FinancialsupportfromtheCEGA-VisaFinancialInclusionLabisgratefullyacknowledged.TheviewsexpresseddonotreflecttheviewsoftheWorldBank.Allerrorsaremyown. †DevelopmentImpactEvaluation,WorldBank Contents 1Introduction2 2Consumersurpluswithincompletefinancialmarkets6 2.1Model.......................................7 2.1.1Environment...............................7 2.1.2Existenceofmodelsolutions.......................9 2.1.3Graphicalrepresentationofthemodel..................9 2.2Roy’sidentity11 2.3Consumersurplus12 2.3.1Equivalentvariation12 2.3.2Marshalliansurplus14 2.3.3Uncompensatedandcompensateddemandelasticities14 2.4Extensions16 3Practicalguidanceonconsumersurplusfromfinancialtechnologies16 3.1Defining,estimating,andgraphingdemandforfinancialtechnologies17 3.2Simplifyingassumptionsondynamicallycompensateddemand18 3.3Extensions21 4Consumersurplusfromsavingsandmicrofinance23 4.1Retirementsavings(Dufloetal.,2006)23 4.1.1Contextandexperimentaldesign23 4.1.2Demandelasticitiesandconsumersurplus25 4.2Commitmentsavings(Karlan&Zinman,2018)27 4.2.1Contextandexperimentaldesign27 4.2.2Demandelasticitiesandconsumersurplus28 4.3Microfinance(Karlan&Zinman,2019)30 4.3.1Contextandexperimentaldesign30 4.3.2Demandelasticitiesandconsumersurplus32 4.4Discussionofresults36 5Conclusion38 1Introduction Whatarethehouseholdwelfaregainsfrommicrofinance?Morethan200millionhouseholdsborrowfrommicrofinanceinstitutionsannually.Despitethisscale,agrowingempiricalconsensusholdsthatmicrofinancehasfailedtomeetitsoriginalpromise,insteadofferingpositivebutmodestimpactsonborrowers(Banerjeeetal.,2015b;Meager,2019).However,estimatingwelfaregainsisdifficult.Householdsmaybenefitfrommicrofinancethroughabroadrangeofmechanisms–microfinanceenablesproductiveinvestmentsandlumpypur-chases(Banerjeeetal.,2021),consumptionsmoothing(Lane,2020),andactsasagatewaytotraditionalcredit(Rigol&Roth,2021).Asaresult,thesignandmagnitudeofimpactsofmicrofinanceoncommonwelfareproxies,includinghouseholdconsumption,maybein-consistentwithimpactsonwelfare(Banerjeeetal.,2015b),andtheoryaccountingforthesediversemechanismsisnecessarytoquantifyimpactsonwelfare(Karlan&Zinman,2019). Inthispaper,Iproposeamethodtoestimatethehouseholdwelfaregainsfromfinancialtechnologies,includingmicrofinance,thatbuildsonthefollowingresult:consumersurplusisequaltotheareaunderdynamicallycompensateddemand.Tocapturethecomplexityofhouseholdconsumptionandinvestmentdecisionsindevelopingcountries,Idevelopadynamichouseholdmodelwithincompletefinancialmarketsandgeneraltechnology,pref-erences,andchoicesets.Ishow