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语言文化论文-AGING AND PRODUCTIVITY AMONG ECONOMISTS.doc

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语言文化论文-AGING AND PRODUCTIVITY AMONG ECONOMISTS.doc

语言文化论文AGINGANDPRODUCTIVITYAMONGECONOMISTSAbstractEconomistsproductivityovertheircareersandasmeasuredbypublicationinleadingjournalsdeclinesverysharplywithage.Thereisnodifferencebyageintheprobabilitythatanarticlesubmittedtoaleadingjournalwillbeaccepted.Ratesofdecliningproductivityarenogreateramongtheverytoppublishersthanamongothers,andtheprobabilityofacceptanceisincreasinglyrelatedtotheauthorsqualityratherthantheauthorsage.Itiswellknownthatproductivitydeclineswithageinawiderangeofactivities.Lehman1953suggestsanearlypeakinproductivityinavarietyofscientificandartisticendeavors,andDiamond1986documentsthepatternforseveralscholarlypursuits.LevinandStephan1992provideclearevidencethatthisdeclineexistsevenaftercarefulattemptstoaccountforindividualandcohortdifferences.Fair1994findsdeclinesinphysicalabilityamongeliterunners,asdoesLydall1968,pp.113passiminphysicalabilitiesofthepopulationgenerally.Inthisstudyweexamineproductivitydeclinesinourownfield.Themainnewresultsarisefromouruseoftwodifferenttypesofinformation,theequivalentofhouseholdandestablishmentdata,tostudythestonefieldoveressentiallythesameperiodoftime.SectionIdiscussesthegeneralresultsonagingandproductivity,whereassectionIIpresentsevidenceoftheimportanceofheterogeneity.I.DecliningProductivitywithAgeUsingtheAmericanEconomicAssociationAEADirectoryofMembers,weidentifiedtenuredeconomicsfacultyat17topresearchinstitutionsandobtainedtheyearsoftheirPh.D.degrees.1WiththecitationindexoftheJournalofEconomicLiteraturewereplicatedportionsofthecurricalavitaeofeachofthe208economistscurrentlyintheeconomicsdepartmentsofthoseinstitutionswhoreceivedPh.D.degreesbetween1959and1983.2Tomeasureproductivityweconstructthreeindexes,combiningpaperspublishedinrefereedjournals.Priorresearchsuggeststhat,atleastintermsofsalarydetermination,thereturnsfromnonreferredpublicationsarequitelowSauer1988,sothatweignoresuchpublicationsincalculatingthesemeasures.I1weightsanarticlebythejournalwhereitappearsbasedoncitationstothatjournal,usingvaluesgeneratedbyLabandandPiette1994.Thisindexdistinguishesstronglyamongjournals.Forexample,theJournalofPoliticalEconomyhasaweightof59.1,whereasEconomicInquiryhasaweightof7.9.InconstructingI1weusetheweightsassociatedwiththedecadeinwhichthearticleswerepublished.I2distinguishessomewhatlessamongjournalsbyassigningallarticlesintheninecorejournalsidentifiedbyLabandandPietteavalueof1,whereasallotherjournalsarevaluedat0.5.3Finally,I3givesallpapersaweightof1.Coauthoredarticlesweregivenhalfcredit,consistentwithSauers1988findingsontheeconomicreturnstocoauthorship.4Wemeasurethechangeinproductivityoverthelifecyclebythepercentagechangeinthenumberofpublicationsfrom910yearspastthePh.D.totheperiods1415yearsandthen1920yearsafter.Formostoftheeliteeconomiststhebaseperiodisequivalentaccountingforpublicationlagstothetimeoftenure,whenonemightexpectthatincentivestoproduceareatapeak.Usingtwoyearpublicationrecordsateachpointreducestheeffectsofnoiseintheperformancemeasures.Onemightarguethatstillotherscientificlifecyclemilepostse.g.,attainingafullprofessorshipshouldbeaccountedfortooandtosomeextentthe1415yearpointdoesthis.Butourmainpurposeissimplytoprovidedetailedevidenceontherelationshiptoage,andourdataarenotsufficienttoinfertheimpactofeverypossiblemilepost.Table1containsdataonproductivitylossbyPh.D.vintagemeasuredbyeachofthethreeindexes.IfweconsiderI1andI2,thetwoindexesthattakejournalqualityintoaccount,thedeclineappearstobequitesubstantial.Betweenyears910and1415eliteeconomistsasagrouplose29to32oftheiroutput.Fromyears910to1920theylose54to60.Inotherwords,productivitylossesareontheorderof5peryearfromthetimeofpeakproductivity.However,thelossesdonotappeartoaccelerateoverthese10yearsoftheeconomistsworklives.Thelossfromyear10toyear20isapproximatelytwicethatfromyear10toyear15.Anotherwaytostudytheageproductivityrelationshipistoexaminejournalsratherthanindividuals.Thefirstrowineachpairofyearsintable2showstheagesofauthorsoffulllengthrefereedarticlesinseveralleadingjournalsAmericanEconomicReview,JournalofPoliticalEconomy,andQuarterlyJournalofEconomics.5Themedianageofauthorsinthe1980sand1990swas36.Scholarsoverage50whentheirstudiesarepublishedareaminutefractionofallauthorsinthesejournals.Creativeeconomicsatthehighestlevelsismainlyfortheyoung.Thatisastrueinthe1990sasitwasinthe1960s,althoughtheagedistributionofauthorsdoesseemtohaveshiftedslightlyrightwardinthelate1970s.Thesecondrowineachpairintable2showstheagedistributionsofrandomsamplesofthemembershipoftheAmericanEconomicAssociationinyearsnearthoseforwhichtheauthorsagesweretabulated.6Thedistributionsareheavilyconcentratedbetween36and50.DecadalvariationsreflectrapidexpansionofAmericanuniversitiesinthemiddleandlate1960s,stagnationinthe1970sandmuchofthe1980s,andapossiblefragmentationoftheprofessioninthe1980sasspecializedassociationsexpanded.AsubstantialpercentageofAEAmembersisoverage50implyingthatoldereconomistsaregreatlyunderrepresentedamongauthorsinmajorjournalsrelativetotheirpresenceamongthosewhoviewthemselvesaspartoftheeconomicsprofession.7AmongtheseveralgroupsofphysicalscientistsanalyzedbyLevinandStephan1992thedeclineofproductivityhighqualitypublishingwithagewasverypronounced.McDowells1982smallsamplesofscholarsinavarietyofdisciplinessuggestlessrapiddeclinesinproductivitywithageinpublicationsunweightedbyquality,withthesharpestdeclinesandearliestpeaksinthehardsciences,andlaterpeaksamongEnglishprofessorsandhistorians.Theevidencefromourtwoverydifferenttypesofsamplesofeconomistsandeconomicspublishingthataccountforthequalityofpublicationssuggeststhat,forwhateverreason,economicsisatleastasmuchayoungpersonsgameasarethephysicalsciences.II.HeterogeneityinDecliningProductivityTheevidenceinsectionIdocumentsthedeclineinproductivityatthesamplemeans.Informationontheageproductivityrelationshipattheextremesofthesampleisinterestinginitsownrightandmighthelpshedsomelightonthepossiblecausesoftheapparentdeclineinproductivitywithage.Thesimplesttestcomparesproductivitylossesamongthetopearlyperformerswiththatoftheentiresampleofeconomistsateliteinstitutions.Amongthetop10ofearlyproducersthemeanvaluesofI1,I2,andI3atyear20were64,50,and22,respectively.Thesemeansarequiteclosetothoselistedfortheentiresampleintable1.Thusonaverageearlypromiseseemstobesustainedinthissample.Ofthe12topresearchersonwhomwehave20yearsofdata,fivewerestillamongthetopdozenproducersatyear20.Theseconclusionsareconfirmedwhenweexaminetheentiresample.ForeachindexIj,j1,2,3,weestimateb0andb1inMultiplelineequationscannotberepresentedinASCIItext.1Table3reportstheparameterestimates.Forallthreeindexesproductivityinyear20ispositivelyandsignificantlyrelatedtoproductivityinyear10.Thereisalsosubstantialproductivityloss.Thejointhypothesisthatb01andb10i.e.,noproductivitylossisrejectedFstatisticsof134,152,and39,respectively.ProductivitylossisleastsevereinI3,whichweightsalljournalsequally,regardlessofquality.IfproductivitylosseswerelessamongeconomistswithhighearlyproductivityhighIj,10,b1wouldbenegative.Infact,fortwoofthethreeindexestheestimatedb1iseffectivelyzero.Wecannotrejectthehypothesisofalinearrelationshipbetweenlateandearlyproductivity.OnlyforI3doesitappearthatproductivitylossishigherfortopearlyproducers,andevenheretheeffectisquitesmall.Aneconomistinthetop10ofthissampleatyear10losesonlyanadditional0.5unweightedpapercomparedtoanaverageresearcherinthissampleatyear10.Theverytopproducersinthiselitesamplekeeponproducinghighqualityresearch,butataslowerrate.Thosewhowerenotatthetopearlyintheircareersslowdownasrapidlyasthetoppeople,buttheirslowdownleadsthemtopublishincreasinglyinlowerqualityoutlets.Anotherwayofexaminingheterogeneityistolookathowauthorsofdifferentqualityfreeinthepublicationprocessconditionalontheirefforts.Weobtaineddataonarandomsampleofinitialsubmissionstoamajorgeneraljournalduringafourmonthperiodin1991.SomeofthedatawereinitiallysuppliedbythejournalsofficeforuseinHamermesh1994.Refereeingatthisjournalisdoubleblind,sothatthechancethatrefereesthoughpossiblynottheeditorswereaffectedbyauthorsreputationsisreduced.Theagesoftheauthorsofthese313papersaremeasuredasof1993toaccountfortheprobabletwoyearaveragelagbetweenthesubmissionofapaperanditspublication.Thesimplefactintheseadditionaldataisthatacceptanceratesatthisjournalareremarkablyconstantbyauthorsage.Theprobabilitiesofanarticlebeingacceptedare0.122,0.114,and0.123inthethreeagegroups50,respectively.8Onaveragethereisnodeclinewithageintheacceptancerateofpaperssubmittedtothisjournal.9ProbitsontheacceptanceofasubmissionthatalsoincludedvariablesindicatingwhethertheauthorwasamemberoftheAEA,wasinatop20departmentaslistedinBlank,1991,wasresidentinNorthAmerica,orwasfemale,andtheauthorspriorcitationrecordyieldanidenticalconclusion.Thedecliningpresenceofolderauthorsintopeconomicsjournalsdoesnotoccurbecauseolderauthorswhokeepsubmittingpaperssufferhigherrejectionrates.Theprobitsincludedinteractiontermsbetweenindicatorvariablesforageandtheextentofcitations.Lowcitedeconomistsweredefinedasthosewithfewerthan10citationsperyear,wellcitedwithatleast10.Asfigure1clearlyshows,acceptanceratesforeachagegroupdiffersharplybycitationstatus.Comparingauthorsage3650tothoseover50,itisquiteclearthatthedegreeofheterogeneityincreaseswithage.Thisappearstobelesstrueincomparingtheoldesttotheyoungestgroup,butthatinferenceisduemainlytoaverysmallsample.Onlysixauthorsunderage36,thefuturesuperstarsoftheprofession,werewellcited.Thegeneraltenorofthecombinedresultsfromthissampleisthattheprofessionsignalstolessablescholarsthattheirworknolongermeetstheprofessionshigheststandards,andmostofthemrespondbyreducingtheirsubmissionstothehighestqualityjournals.III.ConclusionsWehavefollowedthecareersofeconomistsandmeasuredthedemographiccharacteristicsofpublishersinleadingjournals.Theevidenceseemsquiteclearthatpublishingdiminisheswithage,especiallypublishinginleadingjournals,atratesasrapidasinthephysicalsciences.Indeed,remarkablyfewolderpeoplepublishsuccessfullyinthescholarlyoutletsonwhichtheprofessionplacesthehighestvalue.Aseconomistsage,thosewhowerethemostproductiveearlyintheircareersareamongthefewsurvivorsstillcontributingtoscholarshipthroughtheleadingscholarlyoutlets.Whetherthisrelationshipisduetonaturaldeclinesincapacityordecreasedincentivestoproduceisextremelydifficulttodiscern.Unlikeathletes,whereitislikelythatpurephysicaldeteriorationcausesthereductioninproductivitywithage,amongscholarseventhefairlysubtlefactsthatwehaveuncoveredcanbemarshaledassupportforeachofthesecompetinghypotheses.Withoutdirectobservationonhowscholarsuseoftimechangesastheyage,weareunlikelytobeabletodistinguishbetweenexplanationsofthedecliningageproductivityrelationshipinscience.

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