公司多元化经营外文文献及文献综述毕业论文

本份文档包含：关于该选题的外文文献、文献综述一、外文文献标题:Theeffectsofinstitutionalownershiponthevalueandriskofdiversifiedfirms作者:MohammadJafarinejada, SurendranathR.Joryb,ThanhN.Ngoc,期刊:InternationalReviewofFinancialAnalysis(Volume402015):207-219年份:2015TheeffectsofinstitutionalownershiponthevalueandriskofdiversifiedfirmsAbstractWestudythelinkbetweeninstitutionalownershipandfirms'diversificationstrategy,valueandrisk.OursampleincludesUS-listedfirmswithsegmentdatafrom1998to2012.Wefindthatnotallkindsofdiversificationarevalue-destroying;unlikeindustrially-diversifiedfirms,globalsingle-segmentfirmsaretradingatapremiumrelativetotheirimputedvalue.Thepresenceofinstitutionalinvestorsandthestabilityoftheirshareholdingspositivelyinfluencethelikelihoodthatafirmisdiversified.Theproportion(volatility)ofinstitutionalownershipishigher(lower)amongdiversifiedfirmscomparedtodomesticsingle-segmentfirms.Moreimportantly,thehighertheproportionsofinstitutionalshareholdings,thehighertheexcessvalueofthediversifiedfirmandthelowerthefirmidiosyncraticrisk.Institutionalownershipvolatility,ontheotherhand,isinverselyrelatedtoafirmexcessvaluebutpositivelyrelatedtoitsidiosyncraticrisk.Thus,thepresenceoflong-termstableinstitutionalinvestorsenhancesthevalueofdiversifiedfirms.Ourfindingsremainrobusttovariousmodelspecificationsandestimationtechniques.Keywords: Institutional ownership; Corporate diversification;Diversificationdiscount;IntroductionTheeffectofdiversificationonfirmvaluecontinuestoattractconsiderableresearchinterest.Therearetwomaintypesofdiversification:product-andgeographicdiversification(Vachani,1991andMartin,2008).Productdiversificationreferstothedegreetowhichfirmsareinvolvedindifferentindustries(werefertothemasbusinesssegments).Geographicdiversificationreferstotheextenttowhichfirmsareinvolvedindifferentcountries(werefertothemasgeographicsegments).Bodnar,Tang,andWeintrop(1997)findthatglobaldiversificationisassociatedwithhigherfirmvalue.Incontrast,Denis,Denis,andYost(2002)findthatdiversificationdecreasesfirmvalue.OtherstudiesthatsuggestthatdiversificationadverselyaffectsfirmvalueincludeBergerandOfek(1995),Fauver,Houston,andNaranjo(2004);andKimandMathur(2008).Corporatediversificationisappealingtoinvestors.Underthepremisethatcorporationsarebetteratdiversificationthanshareholders,corporatediversificationshouldlowershareholders'investmentriskatafractionofthecostincurredbyindividualinvestors(seeAgmonandLessard(1977);DoukasandTravlos(1988);HarrisandRavenscraft(1991);SandersandCarpenter(1998)).However,thediversityofoperationsatconglomeratefirmsmakesitharderforordinaryinvestorstomonitorthem(Fatemi,1984),openingthepossibilityformanagementtopursueself-interestobjectivesattheexpenseoftheshareholders(Palich,Cardinal,&Miller,2000).Suchagencyproblemswillreduceshareholders'returnoninvestmentincreasetheirrisk.Asaconsequence,ifthereisagroupouttherewhoisbetteratmonitoringmanagers,itisbettertofollowtheirlead.JensenandMeckling(1976),andShleiferandVishny(1986)suggestthatlargeinvestorscouldwellbethatgroup.Weproposetoconsiderthecontributiontofirmvalueandriskbroughtaboutbysuchanimportantgroupofinvestorsatdiversifiedfirms,i.e.,institutionalinvestors.Institutionalinvestors—includingmutualfunds,hedgefunds,pensionfunds,banksandinsurancecompanies—areleadingplayersinthefinancialmarketsaswellastheprimaryownersofUScorporateequity(Gillan&Starks,2000).EstimatesoftheirshareholdingsatUSfirmsrangefrom35%inthe1980sand60%inthe2000sto66%bytheendof2010.Giventhesizeoftheirequityinvestments,theytendtoexertconsiderablepressureonmanagementtocreatewealthforinvestors(seealso,ShleiferandVishny(1986)).JarrellandPoulsen(1987),Brickley,Lease,andSmith(1988);AgrawalandMandelker(1990)suggestadirectlinkbetweeninstitutionalinvestorsandshareholders'wealth.Consequently,managerspayalotofattentiontomeetthefinancialtargetssetbytheseinvestors(EasleyandO'hara,1987,Kyle,1985andClay,2002).Actionstakenbytheinvestorstendtogeneratealotofpressandmediaattention,especiallyatlargeanddiversifiedfirms.Manyinstitutionalinvestorsbelievethatdiversifiedfirmscangeneratemoreprofitbyrestructuringtheirdivisions;examplesincludecampaignsbyinvestorsdemandingrestructuringatbigfirmslikePepsiCo,Sony,Timken,andMcGraw-Hill.Doinstitutionalinvestors—aseffectivemonitorsoffirmperformance—supportdiversificationandaddvaluetodiversifiedfirmsbyvirtueoftheirpresence?Weattempttoanswerthequestionandanalyzetheimportanceoftwomeasuresofinstitutionalownershipondiversifiedfirms'valueandrisk,i.e.,theproportionofthesharesheldbytheinstitutionalinvestors(IOPr)andtheinstitutionalownershipvolatility(IOV).Thefirstmeasureisextensivelyusedintheliterature,thoughmostlyfocusedondomesticfirms.Anemergingliteratureontheeffectsofinstitutionalownershiponfirmvaluesuggeststhatinadditiontotheproportionofsharesheldbyinvestors,itisequallyimportanttoconsiderinstitutionalownershipstability.Theyarguethatnotallinstitutionalinvestorsstaywithafirmforthelong-term.Someareshort-termandwouldleaveatthefirstsignoftrouble.ElyasianiandJia(2010),andCallenandFang(2013)arguethatinstitutionalinvestorsaremoreincentivizedtomonitortargetfirmsandimproveshareholderwelfare.theextentthatdiversificationdestroysvaluewhileinstitutionalinvestorsaddvalue,wetestwhethertheirpresenceatdiversifiedfirmsaddsvalue.Wehypothesizethatdiversifiedfirmswithhigherproportionsofsharesheldbyinstitutionalinvestors(IOPr)andlowervariabilityintheproportions(IOV)areassociatedwithhigherexcessvalues.Similarly,wepositthatfirmriskisinverselyrelatedtoIOPrandpositivelyrelatedtoManagerswouldbeunderscrutinynottocripplethefirmwithnon-valueaddeddiversificationswhenmoresharesareheldbyinstitutionalinvestors(IOPr).Conversely,ifafirmpursuesthewrongtypeofdiversification,thenthereislittlereasonfortheinvestorstoholdontotheirshares.Thus,weshouldobserveahighervolatilityininstitutionalshareholdings(IOV)amongthissubgroupoffirms.WeexaminetheuniverseoffirmslistedinCOMPUSTATfrom1998to2012.WebreaktheuniverseofCOMPUSTATfirmsintofourgroups:(i)domesticsingle-segmentfirms(DS),(ii)domesticmulti-segmentfirms(DM),(iii)globalsingle-segmentfirms(GS)and(iv)globalmulti-segmentfirms(GM).Wefindthatunlikedomesticfirms,thetrendistogoglobal,i.e.,weobserveafallinthenumberofdomesticfirmsandariseinthenumberofglobalfirmsovertime.Wefindthatnotallkindsofdiversificationareassociatedwithnegativeexcessvalues.Asopposedtoindustrially-diversifiedfirms,globalsingle-segmentfirmstradeatapremiumrelativetotheirmatcheddomesticsingle-segmentfirms.Theidiosyncraticrisklevelsarelowerfordiversifiedfirmscomparedtodomesticsingle-segmentfirms.Theproportionofsharesheldbyinstitutionalinvestors(IOPr)ishigherandthevolatilityinthoseproportions(IOV)isloweratdiversifiedfirmscomparedtodomesticsingle-segmentfirms.Usingprobitregressions,wefindthatthelikelihoodtodiversifyispositivelyassociatedwiththeproportionofsharesheldbyinstitutionalinvestors(IOPr)andinverselyrelatedtoitsvolatility(IOV).UnivariateanalysessuggesttheexistenceofapositiverelationshipbetweenIOPrandfirm'sexcessvalueandaninverserelationshipbetweenIOPrandfirm'sidiosyncraticrisk.Conversely,isinverselyrelatedtoexcessvalueandpositivelyrelatedtoidiosyncraticrisk.Theevidencesuggeststhatthereexistsasignificantrelationshipbetweenthepresenceoflong-termstableinstitutionalinvestorsandtheabilityofdiversifiedfirmstocreatewealth.Consistentwiththeunivariatefindings,thecoefficientofIOPrispositiveandthatofisnegativeinpanelfixed-effectregressionsoffirms'excessvalues.ThecoefficientsofDMandGM,representingdomesticmulti-segmentfirmsandgloballydiversifiedmulti-segmentfirms,respectively,arebothnegativeandhighlysignificant.theotherhand,globalsinglesegment(GS)firmsareassociatedwithhigherexcessvalues.Inregressionsoffirms'idiosyncraticrisk,thecoefficientsofandIOPrarepositiveandnegative,respectively,suggestingthatfirmswithlowerproportionsofequityheldbyinstitutionalinvestorsandhighervolatilityinthatproportionareperceivedasriskierandcarryingmoreidiosyncraticrisk.Overall,theempiricalevidencesuggeststhatdiversifiedfirmvalueislinkedtoinvestorswithconsiderableandstableshareholdings.Furthermore,theabsenceofstable,long-terminstitutionalinvestorsincreasestheidiosyncraticriskofdiversifiedfirms.Ourempiricalfindingsarerobusttoalternativecontrolvariables,variousmodelspecificationsandestimationtechniques.Beyondcomplementingandextendingtheliteratureonthediversificationdiscount,thisstudyalsocontributestotheemergingliteratureontheroleofinstitutionalownershipstabilityonfirmgovernanceandperformance.thebestofourknowledge,ourstudyisthefirsttoassesstheimpactofinstitutionalownershipstabilityamongdiversifiedfirms.Weconsidertheeffectofinstitutionalinvestorsinlesseningthediversificationdiscount.Wealsoexaminethelinkbetweeninstitutionalinvestorsandfirmrisk.Theremainderofthepaperisorganizedasfollows.Section2reviewstheliteratureandformulatesthehypotheses.Section3presentsthedata.Section4presentsthemethodsused.WepresentanddiscussthefindingsinSection5,andconcludethepaperinthefinalsection.LiteraturereviewandhypothesesdevelopmentAtthefirmlevel,institutionalinvestorstendtoresistcounterproductivestrategieswhilesupportingbeneficialones,especiallyshareholderdrivenones(BethelandLiebeskind,1993,HillandSnell,1988,HoldernessandSheehan,1985andMikkelsonandRuback,1991).Theytendtolobbyseniorexecutivestoimplementrestructuringstrategiesthatarebeneficialtoalltheshareholders(seealsoBethelandLiebeskind(1993)).Attigetal.(2012)arguethatlong-terminstitutionalinvestorshavegreaterincentivesandefficiencies—economiesofscaleinthecollectionandprocessingofcorporateinformation—toengageineffectivemonitoring,whichinturnmitigatetheasymmetricinformationdilemmaandassociatedagencyproblems.Barclay,Holderness,andPontiff(1993)findthatinvestorsvaluetheskillsanddemandsofblockpurchasersandthatfirmvalueincreasesfollowingablocktrade.Theydocumentahighturnoverinmanagementfollowingthesetradesandadeclineinfirmvaluewhentheblockholderseitherfailtoachievecontrolfaceresistancefrommanagement.NavissiandNaiker(2006)findthatshareholdingbyactiveinstitutionalinvestorsofupto30%positivelyinfluencescorporatevalue.Beyond30%,theownershiptendstoreducefirmvalue,whichsuggeststhatthereexistsanon-linearrelationshipbetweenthetwo.Whentheseshareholdersbecometoolarge,thereexistsasignificantriskthattheywilljoinforceswithmanagementtosafeguardtheircommoninterestsattheexpenseoftheothershareholders,especiallyminority/individualones.Theauthorsfindthatpassiveinvestorsdonotaffectfirmvalue.Cornettetal.(2007)findthatthepercentagesofinstitutionalinvestorinvolvementinafirm,aswellastheirnumbers,areassociatedwithbetteroperatingcashflowreturns.However,thefindingsonlyholdwhentheinvestorshavenobusinessrelationwiththefirm;elsethereisnosignificantrelationshipbetweeninstitutionalinvestorsandfirmperformance.Intheory,aconglomeratefirmwithmultiplebusinesssegmentsshouldtradeatthesamepriceasthesumoftheindividualsegmentsasstandalonebusinesses.Yet,theliteraturefindsthatthisisrarelythecase.ThisinequalityisduetoasymmetricinformationandagencyconflictsalongthelinesexplainedbyMyers(1984);MyersandMajluf(1984).However,recentstudiesoninstitutionalownershipandstabilitysuggestthatinstitutionalinvestorscanhelpsolvesuchproblems.Westudywhethertheinvolvementofinstitutionalinvestorscanturnthefortunesofdiversifiedfirmsgiventheevidenceofadiversificationdiscount(Fauveretal.,2004,Jory&Ngo,2012).H1.Thereexistsapositiverelationshipbetweendiversifiedfirms'valueandtheproportionofthesharesheldbyinstitutionalinvestors.Nonetheless,notallinstitutionalinvestorsareequallymotivatedtoensurethelong-termwell-beingofafirm.Thereexistsomeinvestorswithaninterestinshort-termtrading,quickprofitsandturnaround.Theyarenotwillingtoincurlong-termmonitoringcostsandarenotinterestedinmonitoringfirm'smanagement.CallenandFang(2013)reviewsomescenariossuggestiveofashort-termbias.thefirstcase,thecostofmonitoringfarexceedsthecombinedcostsofsellingthesharesandinvestinginanothercompany.Second,manyinstitutionalinvestorsholdwell-diversifiedportfoliosthatdonotrequirethemtomonitoractivelyeverycompanyintheirportfolio.Third,thebenefitsofshort-termgainsfarexceedthoseoflong-terminvesting.Withtheirconstantbuyingandselling,theseinvestorscausealotofvariability/volatilityintheproportionofsharesheldbytheminthecompany.Thus,wehypothesizethatforvaluecreation,stableinstitutionalinvestorsaremoredesirablethantransientones.H2.Thereexistsaninverserelationshipbetweenfirmvalueandinstitutionalownershipvolatility.Institutionalinvestorstendtobelargeonesbuyingsignificantstakesinthecompaniestheyinvest.Giventhesizeoftheirinvestments,theypayparticularattentiontotherisk-takingactivityattargetfirms,andtheyhavesufficientinfluencetolobbyseniorexecutivestoswayrisk-takingdecisionsintheirfavor.Wehypothesizethatthepresenceoftheseinvestorswoulddissuademanagersfromtakingexcessiveidiosyncraticrisks—forinstance,engaginginunrelateddiversificationabroadwherethemanagershavelittleknowledgeof,thusincreasingtherisksthefirmfaces.Institutionalinvestorshavetheirownstakeholderstosatisfy—forinstance,pensionfundsandinsurancecompanieshavetomakeregularpaymentstotheirsubscribers—andtheywouldresistchangesthatwoulddisruptthoserelationships.theextentthattheirrequiredreturnoninvestmentislinkedtochangesinthevalueofthefirm,theywouldwithstandactionsthatwouldincreasethevarianceofthefirmreturnsandadverselyaffectitsabilitytopaydividend.Thiswouldalsobetrueforinstitutionalinvestorswhohaveselectedtargetsbasedontheircurrentbusinessstrategiesandaresatisfiedwiththestatusquo;thosewholacktheexpertiseincentivestomonitornewventuresandriskyundertakings;and,investorswhosewealthisconcentratedinthetargetcompany.Therearetwotypesofrisksfacedbyafirm,i.e.,marketandidiosyncraticrisks.Managementcanmoredirectlyaffectthelatter.Thus,forthepurposeofourstudy,weconsiderafirm'sidiosyncraticrisk.minimizeitsimpactonthevalueoftheirequityinvestment,wetestthehypothesisthatthepresenceofinstitutionalinvestorshelpstominimizeidiosyncraticrisk.H3.Thereexistsaninverserelationshipbetweenfirmidiosyncraticriskandtheproportionofsharesheldbyinstitutionalinvestors.Financialmarketscompriseinvestorsandtradersofdifferenttimehorizons(Malagon,Moreno,&Rodriguez,2015).Investorsengaginginfrequenttradingaremoreinterestedinshort-ratherthanlong-termgains.Theycouldlobbyformakeshiftcorporatechangesattheexpenseofchangesthatwouldhavebenefitedalltheshareholdersinthelongrun.Theirpresencewillalsodolittleinalleviatingtherisksassociatedwithmisalignmentofobjectives,opportunisticbehaviorandearningsmanagementattheinvesteefirmand,consequently,accentuatethefirm'sidiosyncraticrisk.Frequenttradinginthesharesofafirm—causedbyshort-termtraders—willleadtoanincreaseinthevolatilityoftheproportionsofsharesheldbyitsinvestors.Conversely,long-terminvestors—thosewhoaremorelikelytobuyandholdandcauselessvolatilityintheproportionsofsharesheldbyinvestors—aremoreincentivizedtomonitorfirmactivitiesandimproveshareholdervalue.Thus,wetestthehypothesisthatthereexistsapositiveassociationbetweenthevolatilityintheproportionsofsharesheldbyinvestorsandafirm'sidiosyncraticrisk.H4.Thereexistsapositiveassociationbetweenfirmidiosyncraticriskandinstitutionalownershipvolatility.DataOursampleoffirmsisfromtheCOMPUSTATdatabaseandoursampleperiodstartsin1998andendsin2012.WedefineadiversifiedfirmasonethatreportsdataontheindustrygeographicsegmentsintheCOMPUSTATsegmentdatatapes.SimilartoHe(2009),westartthesampleperiodin1998becausetheFinancialAccountingStandardsBoard(FASB)issuedSFAS131in1997,whichsignificantlyaffectsthewaybusinessesreportsegmentdata.Following,weexcludethefollowingfirmsfromoursample:(i)firmswithSICcodes(i.e.,utilityfirms)and(i.e.,financialfirms)sincetheyareheavilyregulated;(ii)firm-yearobservationswithsegmentsaleslessthan$20million;and(iii)firm-yearobservationswherethedifferencebetweenthetotalsalesofallitssegmentsandthereportedtotalsalesfortheentirefirmisgreaterthan1%.WefurtherobtainaccountingandfinancialdatafromCOMPUSTAT,ownershipdatafromThomsonFinancialandstockpricedatafromtheCenterforResearchinSecurityPrices(CRSP)databases.TheThomsonFinancialdatabasereportsinstitutional13Fcommonstockholdingsandtransactions.includescommonstockholdingsandtransactionsofinstitutionalmoneymanagerswhereholdingsofthemanagingcompany/filer'slevelareasperthe13Ffilingitself.ItcoversallNYSE,AMEX,NASDAQcommonstocksandincludesallmanagersfiling13FreportswiththeSEC.WepresentthesampledescriptivesinTable1.Webreakthesampleintofourgroupsasfollows:domesticsingle-segment(DS,i.e.,notdiversified),domesticmulti-segment(DM,i.e.,industriallydiversifiedonly),globalsingle-segment(GS,i.e.,geographicallydiversifiedonly)andglobalmulti-segment(GM,i.e.,bothindustriallyandgeographicallydiversified).Thetrendistowardmoregloballydiversifiedfirms;from18%in1998,theirproportionasapercentageoftheentiresampleincreasesto33%by2012.Wehave53,481firm-yearobservationsobtainedfrom11,882firmsdistributedasfollows,63%DS,12%DM,15%GSand10%GMfirms.MethodologyMeasuringexcessvalueexplorethevaluationconsequencesofdiversification,weusethesamemeasureofexcessvalueasinBergerandOfek(1995);andBodnaretal.(1997).Theexcessvalueoffirmiiscalculatedasthenaturallogoftheratioofthefirm'smarketvaluetoitsimputedvalue.Measuringidiosyncraticriskcompute a firm's idiosyncratic risk we use theFama and French,1992andFamaandFrench,1993modelandaddtheexcessreturnonaworldportfoliototheequationasfollows(seealsoStulz(1999)):ResultsProbitregressionsWemodelafirm'spropensitytodiversifyasafunctionofthecharacteristicsofthefirm,itsindustry,itsmacroeconomicenvironmentand,moreimportantly,theinstitutionalownershipvariablesofIOPrandTable2reportstheprobitestimatesfromtwodifferentmodels.Model(1)containstheIOPrvariablewhileModel(2)containsboththeIOPrandtheIOVvariables.valueofthecoefficientrepresentingthevariableIOPrispositiveandstatisticallysignificant.Conversely,thevalueofthecoefficientisnegativeandstatisticallysignificant.ThemarginaleffectsofIOPrandarepositiveandnegative,respectively.Thus,diversifiedfirmsareassociatedwithhigherproportionsofinstitutionalownershipandlowervolatilityinthatratioovertime.Wealsofindthattheoddsthatafirmisdiversifiedarepositivelyassociatedto:firmsize(ln(AT)),profitability(EBITS),beinglistedonamajorUSstockexchange(MAJOR),thenumberofdiversifiedfirmsintheindustry(NUMDIVF),theproportionofsalesgeneratedbydiversifiedfirms(PrINDS),andthenumberofM&Asoccurringintheindustry(NUMA).Conversely,capital-intensivefirms(CAPX),growthfirmsasmeasuredbytheQratio,aswellasgrowthindustries(INDUSTRYQ),growthinGDP(GDPGr)andtheindustry'sdollaramountofdeals(VOLMA)areinverselyrelatedtoafirm'spropensitytodiversify.ExcessvalueandidiosyncraticriskofdiversifiedfirmsWepresentthemeanandmedianexcessvaluesofindustrially-(i.e.,DM,GM)andgeographicallydiversified(i.e.,GS,GM)firmsinTable3.WecomparetheexcessvaluestothatofthesampleofDS(i.e.,domesticsingle-segment)firmsandvariousportfolioscomprisingDSfirms.MorepreciselyandfollowingVillalonga(2004),wecalculateeachfirm'spredictedprobabilitytodiversifyusingtheprobitmodelofEq.Foreachdiversifiedfirm,weformaportfoliocomprisingdomesticsingle-segmentfirmswithprobabilityvaluesfromthesamequartile.Sinceweruntwoversionsoftheprobitmodel,wepresentourfindingsbasedontwoportfoliosofmatcheddomesticsingle-segmentfirms(i.e.,portfolios1and2,respectively)foreverydiversifiedfirm.TheexcessvaluesofDM(meanof−8.20%inPanelA)andGM(meanof16.20%inPanelC)firmsaresignificantlylowerthanthecorrespondingvaluesofbothportfoliosofmatcheddomesticsingle-segmentfirms.Thus,industrialdiversificationisassociatedwithlowerexcessvalues.Conversely,theexcessvaluesofglobalsinglesegmentfirms(GSfirmsinPanelB)arepositiveandsignificantlyhigherthanthoseofdomesticsingle-segmentfirms.OurfindingsareconsistentwithDenisetal.(2002),KimandMathur(2008);andJoryandNgo(2012).Wealsocomparetheidiosyncraticrisksofthefourgroupsoffirms.Theidiosyncraticriskmeasuresofthediversifiedfirms(i.e,DM,GSandGMfirms)areallsignificantlylowercomparedtoeitherthesampleofdomesticsingle-segmentfirmsormatchingportfoliosofdomesticsingle-segmentfirms.Thecombinationofdifferentbusinessgeographicunitsleadstoaportfolioeffectthatdampenstheindividualriskofeachunitcausingadiversifiedfirmtoreportlowerriskmeasures.Thepercentageofsharesownedbyinstitutionalshareholders(IOPr)andthevolatilityofinstitutionalownership(IOV)WepresentthevaluesofandbydiversificationtypeinTable4.WecomparethefigureswithvarioussubsamplesofDMfirms.ThemeanandmedianIOPrfiguresare21%and7%,respectivelyfordomesticsingle-segmentfirms,i.e.,non-diversifiedfirms.contrast,theproportionofcompanysharesheldbyinstitutionalinvestorsishigheramongdiversifiedfirms(bothindustrially-andgeographically-diversifiedfirms).Forinstance,themeanvaluesofIOPratDM,GSandGMfirmsare39%,52%and56%,respectively.Thecorrespondingmedianfiguresare38%,57%and64%,respectively.Thus,institutionalinvestorsholdahigherproportionofthesharesatdiversifiedfirmswhencomparedtonon-diversifiedones.6ConclusionWhilesingle-segmentdomesticfirmsstilldominatethecorporatelandscape,weobserveagradualdeclineintheirnumbersandanincreaseinthefrequencyofglobally-diversifiedfirms.Wefindthatnotallkindsofdiversificationarevalue-destroyingandthatglobalsingle-segmentfirmstradeatapremiumcomparedtomatcheddomesticsingle-segmentfirms.Industrially-diversifiedfirmsthough(eitherdomesticorglobal)areassociatedwithlowerexcessvalues.Nonetheless,thecombinationofthedifferentbusinessgeographicunitsexertsaportfolioeffectthatcausestheoverallenterpriserisktodeclinecausingdiversifiedfirmstoreportlowerriskmeasurescomparedtodomesticsingle-segmentfirms.Weprovideempiricalevidencethatinstitutionalownershipisacorevaluedriverofdiversifiedfirms.Theyareassociatedwithhigherlevelsofinstitutionalshareholdingsandmorestableshareholdingsovertime.Theproportionandstabilityofinstitutionalownershiparepositivelyrelatedtofirmvalueandinverselyrelatedtoitsidiosyncraticrisk.Ourresultsindicatethatthepresenceoflong-termstableinstitutionalinvestorsisasourceofvaluefordiversifiedcorporations.二、文献综述公司多元化经营文献综述摘要公司多元化经营的相关问题是近年来公司战略管理、产业经济学和公司金融领域的一个研究热点，也是一个在理论界颇具争议的话题。国内外学者对此进行了大量的理论和实证研究，但至今未得出一致的结论。本文就国内外关于多元化经营与企业绩效的理论和实证研究成果进行综述，以期为该领域的进一步研究提供有益的线索。关键词：多元化经营；企业绩效；文献综述1引言对于多元化经营的研究最早起源于西方国家，美国学者H.I.Ansoff在20世纪50年代首次提出“多元化经营”这一概念，随后世界各国的研究学者们开始广泛关注。到了60年代，多元化经营开始走向顶峰，西方国家出现的混合并购浪潮推动着多元化经营迅猛发展，但这种发展趋势并未持续太长时间，随着许多实施多元化经营的企业出现资源分配不合理等问题，企业的经营状况日益恶化，企业开始考虑是否应该继续选择这一经营战略。自此以后，企业逐渐转向“归核化经营”。我国企业实施多元化经营战略较西方国家起步晚，我国市场经济的不断完善、改革开放的进一步推动才逐渐使企业对多元化经营感兴趣。我国企业真正开始关注多元化经营问题是在20世纪90年代初期，而今多元化经营在我国企业的战略选择中越来越占据重要地位，当然，我国企业在实施多元化经营的过程中也出现了大量经营失败的情况。但是我国的多元化进程不同于西方国家，大多数企业仍继续坚持以多元化经营为主要的发展战略。我国学术界对于多元化经营的实证研究时间不长，在已有的相关文献中大多数侧重于对“多元化经营与企业绩效的关系”的实证检验，且得到的研究结果并不一致。目前国内学者对多元化经营的研究方法仍有不足，更缺乏较深层次地研究。2国外的研究学术界对多元化与企业绩效进行的研究主要包括多元化程度与绩效、多元化类型与绩效、代理成本与企业绩效三个方面。2.1多元化程度与绩效.多元化程度与绩效研究者们使用了不同的多元化程度的衡量指标和绩效衡量指标，得出了不一致的研究结论。Gort(1962)第一个研究了多元化企业的获利性。他通过企业的业务单元数量、专业化比率以及业务单元数量和专业化比率的乘积这三种计量指标来衡量多元化的程度，分析了1947年～1957年美国111家大公司的情况。其结果表明企业多元化与投资报酬率之间基本不存在相关性。Raverscraft(1983)以1975年的258家公司为样本，用Herfindahl指数计量多元化程度，结果表明企业多元化程度与边际毛利率之间不存在显著的相关性。多数实证研究表明多元化程度的增加会降低企业绩效。Langz(1994)利用Compustat数据库提供的数据分析了多元化对TobinQ值的影响，结果发现Q值与公司多元化之间呈负相关关系。Be