2011諾貝爾經(jīng)濟(jì)學(xué)獎(jiǎng)獲獎(jiǎng)演說英文

AwardCeremonySpeechPresentationSpeechbyProfessorPerKrusell,MemberoftheRoyalSwedishAcademyofSciences,ChairmanoftheEconomicsSciencesPrizeCommittee,10December2011YourMajesties,YourRoyalHighnesses,Laureates,LadiesandGentlemen,sinflatioOurnationaleconomiesarecontinuouslyexposedtochangesintheworldaroundus.Fluctuationsintheeconomicactivityofothercountriesinfluenceforeigndemandforourproducts;variationsinthepricesofrawmaterialsinfluenceourproductioncosts;technicalinnovationschangethemixofgoodsandservicesdemanded.Evaluatingalternativeresponsestothesesortsofinevitableeconomicdisturbancesisacentraltaskforpolicymakers.Howmuch,forexample,wouldaparticularincreaseininterestratesordecreaseinincometaxesaffectthenation'employment?Andhowlongbeforethoseeffectswouldberealised?sinflatioMacroeconomicquestionslikethesearehardtoanswer,becausetheyarefundamentallysocialsciencequestions.Unlikenaturalscientists,economistscannotlookforanswersbyconductingcontrolledexperiments,atleastnotonwholeeconomies.Wemustworkinsteadwiththedataprovidedbyhistory.Inaddition,economiesdonotbehavelikemechanical,naturalsciencesystems.Natureobeysitslawsindependentlyofwhatgovernmentsdecide,buteconomiesdonot,becauseeconomiesconsistofthinkingpeople.Thinkingpeoplearealsoinfluencedbyexpectationsaboutthefuture.Forthisreason,economiesarealsoinfluencedbyexpectationsoffuturepolicydecisionsnotyetmade.Thismakestheco-variationsobservedinhistoricaldatahardtointerpret.Doesaparticularhistoricalchangeinaninterestrateexplainthesubsequentchangeintheinflationrate?Oristhecausalitythereverse:didtheexpectedpathofinflationgeneratetheinterestratechange?Ingeneral,howcanwedistinguishbetweencauseandeffectinamacroeconomy?ThomasSargentandChristopherSimshaveprovidedpowerfultoolsthatcanbeusedwiththedatatoanswerthatquestion.Theyhavedevelopedmethodsthatletuspreciselydistinguishtheeffectofeconomicpolicychangesfromtheeffectofotherchangesintheeconomicenvironment.Theirworkhasilluminatedtheeffectsofmonetaryandfiscalpolicynotjustforresearchersbutalsoforcentralbankersandfinanceministerseverywhere.ChristopherSimshasfocusedontheeffectsofunexpectedchangesineconomicpolicy.Usingaparticularformoftimeseriesanalysis,so-calledvectorautoregression,hehasshownhowwecanunderstandthedynamicresponseoftheeconomytoanimpulselikeatemporarypolicychange.Suchimpulse-responseanalysisallowsustotrackhow,forexample,anunexpectedloweringoftheinterestrate,engineeredbyacentralbank,canaffectinflationandemploymentovertime.Basedonthiscontribution,wenowknowthatalowerinterestrateimpliesanimmediate,gradualincreaseinproductionandemployment,withamaximaleffectafterabouttwoyears.Butitimpliesnoimmediateeffectoninflationatall.Infact,inflationonlystartstoslowlyincreaseroughlyayearandahalfaftertheinterestratedrop,afterwhichitrecedes.Whatwehavelearnedaboutthisprocessiscriticalforcentralbankersconsideringalternativechangesininterestrates.ThomasSargent'sresearchhasallowedustounderstandtheeffectsofmorepermanentchangesineconomicpolicy,suchasaswitchtonewgovernmentbudgetrules.Thiskindofanalysisrequiresadifferentapproachbecausethehistoricaldataofferfewexamplesofsystematicpolicychanges.Indeed,somepolicychangesbeingconsideredmayneverhavebeenusedbefore.Sargent'sapproachtosuchanalysisreliesoncertainaspectsofthebehaviourintheeconomybeingratherconstant-atleast,notchangingwhenpolicychanges.Examplesofsuchconstantbehavioursarehowpeopletradeoffleisureandworkandhowfirmstradeoffdifferentkindsofproductioninputs.Sargentshowedhowstatisticalmethodscouldbeusedtomeasurethese"universaleconomicconstants"inthehistoricaldataandhowamathematicalmodeloftheeconomycouldbebuiltaroundthem.Withsuchamodel,economistsandpolicymakerscannowconductartificiallaboratoryexperimentsandinvestigatetheeffectsofsystematicmacroeconomicpolicychanges.DearProfessorsSargentandSims:Youhavesuccessfullyconfrontedafundamentalchallengefacingempiricalmacroeconomicresearch:todisentanglecauseandeffectinhistoricaldata.Themethodsyouhavedevelopedarenowcentraltoolsforeconomicresearcherstryingtounderstandhowoureconomiesworkandhowtheyreacttotemporaryandpermanentchangesintheeconomicenvironment.Becauseyourmethodsallowustousehistoricaldatatoidentifythecausaleffectsofchangesineconomicpolicy,theyhavealsobecomeindispensabletoolsforpolicymakersworl