第五讲 奥肯定律与菲利普斯曲线.ppt

第五讲奥肯定理和菲力浦斯曲线 PriceDeterminationandtheProductionFunction Weassumethatlaboristheonlyinput then Output Y ANN EmploymentA LaborProductivity 1 Okun sLaw FromOutputGrowthtoUnemployment Recall Y NY N L 1 u AssumeA 1 Thenweget TheactualrelationbetweenoutputgrowthandthechangeintheunemploymentrateisknownasOkun slaw Fromtheaboverelation wecangetonetoonerelationshipbetweenYandu Changeitslightly wecanobtainwhatweneed arelationbetweenoutputgrowthandthechangeofunemployment ChangesintheUnemploymentRateVersusOutputGrowthintheUnitedStates 1970 2000 Usingthirtyyearsofdata thelinethatbestfitsthedataisgivenby Accordingtotheequationabove Tomaintaintheunemploymentrateconstant outputgrowthmustbe3 peryear Thisgrowthrateofoutputiscalledthenormalgrowthrate Accordingtotheequation outputgrowth1 abovenormalleadsonlytoa0 4 reductioninunemployment fortworeasons Fixedproductionunits e g theaccountingdepartmentofafirm LaborhoardingIncreaseinthelaborforce Usinglettersratherthannumbers Outputgrowthabovenormalleadstoadecreaseintheunemploymentrate ThisisOkun slaw In1958 A W PhillipsdrewadiagramplottingtherateofinflationagainsttherateofunemploymentintheUnitedKingdomforeachyearfrom1861to1957 Hefoundaclearevidenceofanegativerelationbetweeninflationandunemployment Whenunemploymentwaslow inflationwashigh andwhenunemploymentwashigh inflationwaslow oftenevennegative Twoyearslater PaulSamuelsonandRobertSolowreplicatedPhillips exercisefortheUnitedStates thereappearedtobeanegativerelationbetweeninflationandunemploymentintheUnitedStatesalso SamuelsonandSolowbaptizedthisrelationthePhillipsCurve 2 ThePhillipsCurve FromUnemploymenttoInflation ThePhillpscurverapidlybecamecentraltomacroeconomicthinkingandpolicy Itappearedtoimplythatcountriescouldchoosebetweendifferentcombinationsofunemploymentandinflation Theycouldachievelowunemploymentiftheywerewillingtotoleratehigherinflation Ortheycouldachievepricestabilityiftheywerewillingtotoleratehigherunemployment MuchofthediscussionaboutmacroeconomicpolicybecameadiscussionaboutwhichpointtochooseonthePhillipscurve Inthe1970s however therelationbrokedown TherewasbothhighinflationandhighunemploymentinboththeUnitedStatesandmostOECDcountries Arelationreappeared butitwasnowarelationbetweentheunemploymentrateandthechangeintheinflationrate InflationVersusUnemploymentintheUnitedStates 1900 1960 Inflation ExpectedInflation andUnemployment Thisrelationcanberewrittentoestablisharelationbetweeninflation expectedinflation andtheunemploymentrate 2 1 First thefunctionF assumestheform Then replacethisfunctionintheoneabove RecalltheASrelation Rearranginggives Aslongasinflation expectedinflationandthemarkuparenottoolarge aapproximationtothisequationisgivenby ThePhillipsCurve Ifwesetthen 2 2 Thewage pricespiral GivenPet Pt 1 Lowunemploymentattimet Wt Wt Pt Pet 1 Wt 1 Pt 1 Pet 1 Wt 2 Pt 2 andsoon ThisistheoriginalPhillipscurve Mutations Thenegativerelationbetweenunemploymentandinflationheldthroughoutthe1960s butitvanishedafterthat fortworeasons Anincreaseinthepriceofoil butmoreimportantly Achangeinthewaywagesettersformedexpectationsduetoachangeinthebehavioroftherateofinflation Theinflationratebecameconsistentlypositive andInflationbecamemorepersistent Mutations InflationversusUnemploymentintheUnitedStates 1948 1969 Mutations InflationversusUnemploymentintheUnitedStates 1970 2000 Mutations U S Inflation 1900 2000 TheFormationofExpectations Supposeexpectationsofinflationareformedaccordingto TheFormationofExpectations Intheequationabove when equalszero therelationbetweentheinflationrateandtheunemploymentrateis When ispositive theinflationratedependsonboththeunemploymentrateandlastyear sinflationrate When ispositive theinflationratedependsonboththeunemploymentrateandlastyear sinflationrate TheFormationofExpectations When 1 theunemploymentrateaffectsnottheinflationrate butthechangeintheexpectedinflationrate Since1970 aclearnegativerelationemergedbetweentheunemploymentrateandthechangeintheinflationrate TheFormationofExpectations Thelinethatbestfitsthescatterofpointsfortheperiod1970 2000is ChangeinInflationversusUnemploymentintheUnitedStates 1970 2000 TheFormationofExpectations TheoriginalPhillipscurveis ThemodifiedPhillipscurve alsocalledtheexpectations augmentedPhillipscurve ortheaccelerationistPhillipscurve is BacktotheNaturalRateofUnemployment FriedmanandPhelps theunemploymentratecannotbesustainedbelowacertainlevel naturalrateofunemployment Thenaturalrateofunemploymentistheunemploymentratesuchthattheactualinflationrateisequaltotheexpectedinflationrate then BacktotheNaturalRateofUnemployment then Given then Finally assumingthat etiswellapproximatedby t 1 then BacktotheNaturalRateofUnemployment Thenon accelerating inflationrateofunemployment orNAIRU istherateofunemploymentrequiredtokeeptheinflationrateconstant ASummaryandManyWarnings 8 3 VariationsintheNaturalRateofUnemploymentAcrossCountries VariationsintheNaturalRateofUnemploymentoverTime Note andzmaynotbeconstantovertime Ahighunemploymentratedoesnotnecessarilyreflectahighnaturalrateofunemployment VariationsintheNaturalRateofUnemploymentAcrossCountries ChangeinInflationVersusUnemployment EuropeanUnion 1961 2000 HighInflationandthePhillipsCurveRelation Therelationbetweenunemploymentandinflationislikelytochangewiththelevelandthepersistenceofinflation Wheninflationishigh itisalsomorevariable Theformofwageagreementsalsochangeswiththelevelofinflation Wageindexationmechanism HighInflationandthePhillipsCurveRelation Let denotetheproportionoflaborcontractsthatisindexed and 1 theproportionthatisnotindexed Then becomes Theproportionofcontractsthatisindexedrespondsto t whiletheproportionthatisnotrespondsto et When 0 allwagesaresetonthebasisofexpectedinflation equaltolastyear sinflation then HighInflationandthePhillipsCurveRelation When ispositive DeflationandthePhillipsCurveRelation GiventheveryhighrateofunemploymentduringtheGreatDepression wewouldhaveexpectedalargerateofdeflation butdeflationwaslimited ThereasonforthismaybethatthePhillipscurverelationmaydisappearoratleastbecomeweakerwhentheeconomyisclosetozeroinflation Problems Chapter8 Problems2 3 5 TheAggregateDemandRelation FromNominalMoneyGrowthandInflationtoOutputGrowth Intermsofthegrowthratesofoutput money andthepricelevel Accordingtotheaggregatedemandrelation Giveninflation expansionarymonetarypolicyleadstohighoutputgrowth TheMediumRun Summarizing Inthemediumrun ut ut 1and t t 1 Summarizing Summarizing TheMediumRun InflationandUnemploymentintheMediumRun Disinflation Toachievelowerinflation therateofnominalmoneygrowthmustbereduced Hereiswhathappens 9 3 Intheaggregatedemandrelation Then fromOkun slaw Finally accordingtothePhillipscurverelation Butovertime AccordingtothePhillipscurverelation Intheaggregatedemandrelation Then fromOkun slaw Afteradecreaseinnominalmoneygrowth unemploymentfirstincreases buteventually itstartsdecreasing HowMuchUnemployment andforHowLong Disinflation HigherunemploymentApoint yearofexcessunemploymentisadifferencebetweentheactualandthenaturalunemploymentrateofonepercentagepointforoneyear Forexample assumingthat 1 reducinginflationby10 over5yearsrequires5yearsofunemploymentat2 abovethenaturalrate HowMuchUnemployment andforHowLong Thesacrificeratioisthenumberofpoint yearsofexcessunemploymentneededtoachieveadecreaseininflationof1 Forexample if 1 asacrificeratioof1 32meansthata10 disinflationrequires13 2point yearsofexcessunemployment WorkingOutthePathofNominalMoneyGrowth Thistableshowsthepathofnominalmoneygrowthneededtoachieve10 disinflationoverfiveyears WorkingOutthePathofNominalMoneyGrowth ThisfigureshowsthepathofunemploymentandinflationimpliedbythedisinflationpathinTable9 1 ADisinflationPath Expectations Credibility andNominalContracts 9 4 Thissectionexamineshowchangesinexpectationformationmightaffecttheunemploymentcostofdisinflation Twoseparategroupsofmacroeconomistschallengethetraditionalnotionthatpolicycanchangethetiming butnotthenumberofpoint yearsofexcessunemployment ExpectationsandCredibility TheLucasCritique TheLucascritiqueThomasSargentarguedthatinordertoachievedisinflation anyincreaseinunemploymentwouldhavetobeonlysmall Theessentialingredientofsuccessfuldisinflation heargued wascredibilityofmonetary NormalRigiditie