agglomeration economies and transport investment集聚

JOINTTRANSPORTRESEARCHCENTREDiscussionPaperNo.2007-11December2007AgglomerationEconomiesandTransportInvestmentDanielJ.GRAHAMImperialCollegeUniversityofLondonLondon,UnitedKingdomD.Graham2TABLEOFCONTENTS1.INTRODUCTION............................................................................................................................32.AGGLOMERATIONECONOMIESANDTRANSPORTINVESTMENT..................................42.1.Agglomerationandproductivity...............................................................................................42.2.Transportinvestmentandagglomeration..................................................................................63.ESTIMATINGAGGLOMERATIONECONOMIES.....................................................................93.1.Firmdata.................................................................................................................................103.2.Measuringagglomeration.......................................................................................................103.3.Estimatingthelinkbetweenagglomerationandproductivity.................................................114.RESULTS......................................................................................................................................114.1.Productionfunctionestimates.................................................................................................114.2.Applyingtheagglomerationelasticitiesintransportappraisal...............................................134.3.Limitationsoftheapproachandfutureresearchdirections....................................................145.CONCLUSIONS............................................................................................................................15NOTES...................................................................................................................................................16REFERENCES.......................................................................................................................................17APPENDIX1:THETRANSLOGPRODUCTIONINVESEINPUTDEMANDMODEL................20London,August2007D.Graham3ABSTRACTThispaperisconcernedwiththelinksbetweenagglomeration,productivityandtransportinvestment.Ifimprovementsintransportsystemsgiverisetochangesinthemassofeconomicactivityaccessibletofirms,forinstancebyreducingtraveltimesorthecostsoftravel,thentheycaninducepositivebenefitsviaagglomerationeconomies.ThepaperpresentsempiricalresultsfromaneconometricanalysisoftherelationshipbetweenproductivityandaccessibilitytoeconomicactivityfordifferentsectorsoftheUKeconomy.Theresultsshowthatagglomerationeconomiesdoexistandthattheycanbesubstantial,particularlyforservices.Furthermore,theeffectofagglomerationexternalitiesisnottrivialwhenconsideredinthecontextoftransportappraisal.Initialcalculationstypicallyindicateadditionstoconventionaluserbenefitsof10%-20%arisingfromincreasingreturnstoeconomicmass.1.INTRODUCTIONArecentpaperbyVenables(2007)developsatheoreticalmodeltodemonstratesomeimportantlinksbetweentransportprovisionandagglomeration.Heshowsthatif,asurbaneconomictheorysuggests,thereareincreasingreturnstoagglomeration,thentransportinvestmentsmayinducepositiveproductivitybenefitsbyeffectivelyraisingaccessibilitytoeconomicmass.Anysuchagglomerationexternalitiescanbeclassedas`widerbenefits'oftransportinvestmentinthesensethattheyaretypicallynotcapturedinastandardcost-benefitappraisal.Tounderstandthemagnitudeofthepotential`widerbenefits'oftransportinvestmentwefirstneedquantitativeestimatesofreturnstoagglomeration.Inotherwordswerequiresomeempiricalverificationoftheexistenceandmagnitudeoftherelationshipbetweenproductivityandaccessibilitytoeconomicmass.Preferably,wewanttoexaminethisrelationshipseparatelyfordifferentsectorsoftheeconomybecausethebenefitsderivedfromagglomerationareunlikelytobeuniformacrossindustries.ThispaperdescribestheresultsofnewempiricalresearchontherelationshipbetweenagglomerationandproductivityfordifferentsectorsoftheUKeconomy.Italsoconsiderstheimplicationsofagglomerationeconomiesfortheevaluationoftransportinvestment.Theresultsshowthatagglomerationeconomiesdoexistandthattheycanbesubstantial,particularlyforservices.Iftransportinvestmentschangethedensitiesavailabletofirms,forinstancethroughareductionintraveltimesorinthecostoftravel,thentherearelikelytobepositivegainsfromagglomeration.D.Graham4Furthermore,theeffectofagglomerationexternalitiesisnottrivialwhenconsideredwithintheframeworkoftransportappraisal.Initialcalculationstypicallyindicateadditionstoconventionaluserbenefitsof10%-20%arisingfromincreasingreturnstoeconomicmass.Thepaperisstructuredasfollows.Section2reviewstheliteratureonagglomerationandproductivityanddiscussestherelationshipbetweentransportinvestmentandagglomeration.Section3describesthemethodologyusedtoestimateagglomerationeconomies.Empiricalresultsarepresentedinsection4,includingareviewofsomerecentapplicationsofagglomerationbenefitswithintransportappraisal.Co