andExpectations宏观经济学-加州大学-詹姆斯·布

CHAPTER12ThePhillipsCurveandExpectations1Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.QuestionsWhatisthePhillipscurve?HowhasthenaturalrateofunemploymentchangedintheU.S.overthepasttwogenerations?Whatdeterminestheexpectedrateofinflation?Howcanwetellhowexpectationsofinflationareformed--whethertheyarestatic,adaptive,orrational?2Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.QuestionsHowusefulistheaggregatedemand-aggregatesupplyframework--theIS-LMmodelandthePhillipscurve--forunderstandingmacroeconomiceventsintheU.S.overthepasttwogenerations?Howdoweconnectupthesticky-pricemodelwiththeflexible-pricemodel?3Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Okun’sLawOkun’slawshowstherelationshipbetweentheunemploymentrateandrealGDPor4Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheThreeFacesofAggregateSupplyAggregatesupplyrelatesthepriceleveltothelevelofrealGDPAggregatesupplycanalsorelatetheinflationratetothelevelofrealGDPUsingOkun’slaw,aggregatesupplycanalsorelatetheinflationratetotheunemploymentratethisrelationshipisknownasaPhillipscurve5Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveAggregatesupplycanrelatetheinflationratetothelevelofrealGDPTheright-handsideofthisequationcanbesubstitutedintoOkun’sLaw6Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveLetting=2.5/,wegetthePhillipscurveToallowforsupplyshocks,wewilladdanextratermtothePhillipscurve(s)7Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.1-ThePhillipsCurve8Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.2-ThreeFacesofAggregateSupply9Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveTheslopeofthePhillipscurvedependsonhowstickypricesandwagesarethestickierarewagesandprices,thesmallerisparameter,andtheflatteristhePhillipscurveWhenthePhillipscurveisflat,evenlargechangesintheunemploymentratehavelittleeffectonthepricelevel10Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveWheneverunemploymentisequaltoitsnaturalrate,inflationisequaltoexpectedinflationthepositionofthePhillipscurvecanbedeterminedifweknowthenaturalrateofunemploymentandtheexpectedinflationrate11Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveThePhillipscurveshiftsifeitherexpectedinflationorthenaturalrateofunemploymentchangesorifasupplyshockoccursahighernaturalratemovesthePhillipscurvetotherighthigherexpectedinflationmovesthePhillipscurveupadversesupplyshocksmovethePhillipscurveup12Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.3-ShiftsinthePhillipsCurve13Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.AggregateDemandTheaggregatedemandfunctiondevelopedinChapter11showshowrealGDPrelatestotheinflationrateWecanuseOkun’sLawtodevelopanaggregatedemandequationwithunemploymentontheleft-handside14Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.AggregateDemandTheparameteristheproductofthreethingshowmuchthecentralbankraisestherealinterestrateinresponsetoinflationhowmuchrealGDPchangesinresponsetoachangeintherealinterestratehowlargeachangeinunemploymentisproducedbyachangeinrealGDP15Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.EquilibriumLevelsofInflationandUnemploymentTogether,theunemploymentformoftheaggregatedemandrelationshipandthePhillipscurveequationallowustodeterminewhattheinflationandunemploymentrateswillbeintheeconomytheeconomy’sequilibriumiswherethetwocurvescross16Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.4-EquilibriumLevelsofUnemploymentandInflation17Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.EquilibriumTheeconomy’sequilibriuminflationandunemploymentratesdependonthenaturalrateofunemployment(u*)theexpectedrateofinflation(e)supplyshocks(s)thelevelofunemploymentwhentherealinterestrateisatwhatthecentralbankthinksisitslong-runaverage(u0)thecentralbank’stargetlevelofinflation(’)18Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.SolvingforEquilibriumTosolvefortheequilibriumunemploymentrate,substitutethePhillipscurveequationintothemonetarypolicyreactionfunction19Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.SolvingforEquilibriumTosolvefortheequilibriuminflationrate,substitutethemonetarypolicyreactionfunctionintothePhillipscurve20Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ADecreaseinExportsIfexportdemandfalls,andthecentralbankdoesnothing,u0willrisebyu0TheeffectontheequilibriumlevelofunemploymentwillbeTheeffectontheequilibriumlevelofinflationwillbe21Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.5-EffectsofaFallinExports22Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheNaturalRateofUnemploymentUnemploymentcannotbereducedbelowitsnaturalratewithoutacceleratinginflationIfthenaturalrateofunemploymentishigh,expansionaryfiscalandmonetarypolicyarelargelyineffectiveastoolstoreduceunemploymentMostestimatesofthecurrentnaturalrateintheU.S.liebetween4.5and5.0percent23Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.6-FluctuationsinUnemploymentandtheNaturalRate24Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheNaturalRateofUnemploymentFoursetsoffactorsinfluencethenaturalrateofunemploymentdemographytherelativeageandeducationaldistributionofthelaborforceinstitutionslaborunions,workermobility,taxesproductivitygrowthwagegrowthpastlevelsofunemployment25Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.7-RealWageGrowthAspirationsandProductivity26Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ExpectedInflationThenaturalrateofunemploymentandexpectedinflationtogetherdeterminethepositionofthePhillipscurvehigherexpectedinflationmovesthePhillipscurveupward27Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ExpectedInflationTherearethreebasicscenariosforhowinflationexpectationsareformedstaticexpectationsprevailwhenpeopleignorethefactthatinflationcanchangeadaptiveexpectationsprevailwhenpeopleassumethefuturewillbeliketherecentpastrationalexpectationsprevailwhenpeopleusealltheinformationtheyhaveasbesttheycan28Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveunderStaticExpectationsIfinflationexpectationsarestatic,expectedinflationneverchangesthetrade-offbetweeninflationandunemploymentwillnotchangefromyeartoyearIfinflationhasbeenlowandstable,businesseswillprobablyholdstaticinflationexpectations29Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.9-StaticExpectationsofInflation30Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.StaticExpectationsofInflationinthe1960sInthe1960s,thePhillipscurvedidnotshiftupordowninresponsetochangesinexpectedinflationwhenunemploymentwasabove5.5%,inflationwasbelow1.5%whenunemploymentwasbelow4%,inflationwasabove4%TheeconomymovedalongastablePhillipscurve31Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.10-StaticExpectationsandthePhillipsCurve,1960-196832Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveunderAdaptiveExpectationsIftheinflationratevariestoomuchforworkersandbusinessestoignoreitandiflastyear’sinflationrateisagoodguidetoinflationthisyear,individualsarelikelytoholdadaptiveexpectationsinflationwillbeforecastedbyassumingthatthisyearwillbelikelastyearforecastwillbegoodonlyifinflationchangesslowly33Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveunderAdaptiveExpectationsThePhillipscurvecanbewrittenThePhillipscurvewillshiftupanddowndependingonwhetherlastyear’sinflationwashigherorlowerthanthepreviousyear’sinflationaccelerateswhenunemploymentislessthanthenaturalrate34Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.AdaptiveExpectationsExamplethegovernmentpushestheunemploymentratedown2percentagepointsbelowthenaturalrate=1/2lastyear’sinflationrate=4%Thisyear’sinflationrate=4+1/22=5Nextyear’sinflationrate=5+1/22=6Andsoon35Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.11-AcceleratingInflation36Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.AdaptiveExpectationsandtheVolckerDisinflationAttheendofthe1970s,expectedinflationgavetheU.S.anunfavorableshort-runPhillipscurvetrade-offBetween1979andthemid-1980s,FedchairmanPaulVolckerreducedinflationfrom9to3percentperyearThefallininflationtriggeredafallinexpectedinflationthePhillipscurveshifteddown37Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.12-ThePhillipsCurvebeforeandaftertheVolckerDisinflation38Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveunderRationalExpectationsIftheeconomyischangingrapidlyenoughthatadaptiveexpectationsleadtolargeerrors,individualswillswitchtorationalexpectationsPeopleformtheirforecastsoffutureinflationnotbylookingbackwardbutbylookingforwardtheylookatwhatcurrentandexpectedgovernmentpoliciestellusaboutwhatinflationwillbe39Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ThePhillipsCurveunderRationalExpectationsThePhillipscurvewillshiftasrapidlyaschangesineconomicpolicythataffectaggregatedemandAnticipatedchangesineconomicpolicyturnouttohavenoeffectonthelevelofproductionoremployment40Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.GovernmentPolicytoStimulatetheEconomySupposethattheunemploymentrateisequaltoitsnaturalrateandinflationisequaltoexpectedinflationThegovernmenttakesstepstostimulatetheeconomybycuttingtaxesandraisinggovernmentspendingtoreducetheunemploymentratebelowthenaturalrate41Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.13-GovernmentAttemptstoStimulatetheEconomy42Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.GovernmentPolicytoStimulatetheEconomyIfthepolicycomesasasurprise,theeconomymovesupandtotheleftalongthePhillipscurveinresponsetothechangeingovernmentpolicyUnemploymentwillbelower,productionwillbehigher,andtherateofinflationwillbehigher43Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.14-ResultsiftheShiftinPolicyComesasaSurprise44Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.GovernmentPolicytoStimulatetheEconomyIfthepolicyisanticipated,individualswilltakethepolicyintoaccountwhentheyformtheirexpectationsofinflationThePhillipscurvewillshiftupTherewillbenoeffectonunemploymentoroutputTherateofinflationwillrise45Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.15-ResultsiftheShiftinPolicyIsAnticipated46Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.WhatKindofExpectationsDoWeHave?Ifinflationislowandstable,expectationsareprobablystaticIfinflationismoderateandfluctuatesslowly,expectationsareprobablyadaptiveWhenshiftsininflationareclearlyrelatedtochangesinmonetarypolicy,swifttooccur,andlargeenoughtoseriouslyaffectprofitability,expectationsareprobablyrational47Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.FromtheShortRun

totheLongRunInthecaseofananticipatedshiftineconomicpolicyunderrationalexpectations,thelongrunisnowIntheabsenceofsupplyshocksIfexpectationsarerationalandchangesinpolicyforeseen,expectedinflationwillbeequaltoactualinflationandunemploymentwillbeatitsnaturalrate48Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.16-RationalExpectations:TheLongRunIsNow49Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.FromtheShortRun

totheLongRunIfexpectationsareadaptive,theeconomywillapproachthelongrungraduallyanexpansionaryshockwilllowerunemployment,increaserealGDP,andleadtoanincreaseintheinflationrateindividualswillraisetheirexpectationsofinflationinthenextperiodsastimepasses,thegapsbetweenactualunemploymentanditsnaturalrateandactualandexpectedinflationwillshrinktozero50Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure12.17-AdaptiveExpectationsConvergencetotheLongerRun51Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.FromtheShortRun

totheLongRunUnderstaticexpectations,thelongrunneverarrivesthegapbetweenexpectedandactualinflationcangrowarbitrarilylargeasdifferentshockshittheeconomyifthegapbetweenactualandexpectedinflationbecomeslarge,individualswillnotremainsofoolishastoretainstaticexpectations52Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ChapterSummaryThelocationofthePhillipscurveisdeterminedbytheexpectedrateofinflationandthenaturalrateofunemployment(andpossiblybycurrent,activesupplyshocks)intheabsenceofcurrent,activesupplyshocks,thePhillipscurvepassesthroughthepointatwhichinflationisequaltoitsexpectedvalueandunemploymentisequaltoitsnaturalrate53Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ChapterSummaryTheslopeofthePhillipscurveisdeterminedbythedegreeofpricestickinessintheeconomythemorestickyareprices,theflatteristhePhillipscurveThenaturalrateofunemploymentintheU.S.hasexhibitedmoderateswingsinthepasttwogenerations54Copy