曼昆宏观经济学第七版笔记Word格式.docx

曼昆宏观经济学第七版笔记Word格式.docx

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IX.AggregateDemandI32

X.AggregateDemandII38

XI.AggregateDemandintheOpenEconomy44

XII.AggregateSupply50

XIII.ADynamicModelofAggregateDemandandAggregateSupply55

Introduction

QuestionsMacroeconomicswantstoanswer

Whyhavesomecountriesexperiencedrapidgrowthinincomesoverthepastcenturywhileothersstaymiredinpoverty?

Whydosomecountrieshavehighratesofinflationwhileothersmaintainstableprices?

Whydoallcountriesexperiencerecessionsanddepressions—recurrentperiodsoffallingincomesandrisingunemployment—andhowcangovernmentpolicyreducethefrequencyandseverityoftheseepisodes?

MajorMarkets

Goodsandservicesmarket

Moneymarket

Factormarket

Labormarket

Internationalmarket

Data

Majordata

GDP

Inflationrateandmoneysupply

Unemploymentrate

Netexportandexchangerate

Nominalversusrealdata

Models

Abstractionoftherealworld

Mathematicandmodels

Endogenousvariablesandexogenousvariables

Assumptionsofmodels

Structure

ClassicalTheory

Marketclearing

Priceflexibility

GrowthTheory

Emphasisthegrowthofcapital,laborandtechnology

Explainhoweconomyevolvesoverdecades

BusinessCycleTheory

Studyfluctuationinshort-term

Marketisnotclearing

NationalIncomes

GoodsandServices

Factorsofproductionaretheinputsusedtoproducegoodsandservices.

Capital（K）

Labor（L）

Theproductionfunction:

Y=F（K,L）

Constantreturntoscale:

toanyz,

zY=F（zK,zL）

NationalIncomeDistribution

Factorpricesaretheamountspaidtothefactorsofproduction—thewageworkersearnandtherenttheownersofcapitalcollect.

Wage（W）

CapitalRent（R）

Considerlabor,holdingcapitalconstant

Theprofits:

Profits=PY-WL-RK

Themarginalproductoflabor（MPL）istheextraamountofoutputthefirmgetsfromoneextraunitoflabor.

Diminishingmarginalproduct:

holdingtheamountofcapitalfixed,themarginalproductoflabordecreasesastheamountoflaborincreases.

CaseStudy:

TheBlackDeathandFactorPrices

Aswehavejustlearned,intheneoclassicaltheoryofdistribut-ion,factorpricesequalthemarg-inalproductsofthefactorsofproduction.Becausethemargi-nalproductsdependonthequantitiesofthefactors,achangeinthequantityofanyonefactoraltersthemarginalproductsofalltheactors.Therefore,achangeinthesupplyofafactoraltersequilibriumfactorprices.

Fourteenth-centuryEuropeprovidesavividexampleofhowfactorquantitiesaffectfactorprices.Theoutbreakofthebubonicplague—theBlackDeath—in1348reducedthepopulationofEuropebyaboutone-thirdwithinafewyears.Becausethemarginalproductoflaborincreasesastheamountoflaborfalls,thismassivereductioninthelaborforceraisedthemarginalproductoflabor.Realwagesdidincreasesubstantiallyduringtheplagueyears—doubling,bysomeestimates.Thepeasantswhowerefortunateenoughtosurvivetheplagueenjoyedeconomicprosperity.

Thereductioninthelaborforcecausedbytheplaguealsoaffectedthereturntoland,theothermajorfactorofproductioninmedievalEurope.Withfewerworkersavailabletofarmtheland,anadditionalunitoflandproducedlessadditionaloutput.Thisfallinthemarginalproductoflandledtoadeclineinrealrentsof50percentormore.Thus,whilethepeasantclassesprospered,thelandedclassessufferedreducedincomes.

Holdingcapitalconstant,then:

ΔProfit=ΔRevenue-ΔCost=（P×

MPL）-W.

ThecompanywilladdlaboruntilΔProfit=0,atthattime,

MPL=W/P

Copytheprocess,ifweconsidercapital,thecompanywilladdcapitaluntil

MPK=R/P

WecallW/Pasrealwage,andR/Pasrealrentalpriceofcapital.

Theincomethatremainsafterthefirmshavepaidthefactorsofproductionistheeconomicprofitoftheownersofthefirms.

EconomicProfit=Y-（MPL*L）-（MPK*K）.

Iftheproductionfunctionhasthepropertyofconstantreturnstoscale,then,

z*Y=Economicprofits+z*MPL*L+z*MPK*K

Differentiatewithrespecttoz,

F（L,K）=MPL*L+MPK*K

DemandforGoodsandServices

Aclosedeconomyhasthreeusesforthegoodsandservicesitproduces.

Y=C+I+G

Consumption

Disposableincome:

incomeafterthepaymentofalltaxes,Y?

T.

C=C（Y-T）

Marginalpropensitytoconsume（MPC）:

theamountbywhichconsumptionchangeswhendisposableincomeincreasesbyonedollar.

Investment

Thequantityofinvestmentgoodsdemandeddependsontheinterestrate.I=I（r）.

Iftheinterestraterises,fewerinvestmentprojectsareprofitable,andthequantityofinvestmentgoodsdemandedfalls.

GovernmentPurchases（holdingconstant）

Governmentspending

Transferpayments

Equilibrium

EquilibriumintheMarketforGoodsandServices:

Y=C（Y-T）+I（r）+G

EquilibriumintheFinancialMarkets:

S=I

MoneyandInflation

Money

Moneyisthestockofassetsthatcanbereadilyusedtomaketransactions.

TheFunctionsofMoney

Storeofvalue

Unitofaccount

Mediumoftransaction

TheTypesofMoney

Commoditymoney

Fiatmoney

MoneyinaPOWCamp

MoneyandSocialConventionsontheIslandofYapTheeconomyofYap,asmallislandinthePacific,oncehadatypeofmoneythatwassomethingbetweencommodityandfiatmoney.ThetraditionalmediumofexchangeinYapwasfei,stonewheelsupto12feetindiameter.Thesestoneshadholesinthecentersothattheycouldbecarriedonpolesandusedforexchange.

Largestonewheelsarenotaconvenientformofmoney.Thestoneswereheavy,soittooksubstantialeffortforanewownertotakehisfeihomeaftercompletingatransaction.Althoughthemonetarysystemfacilitatedexchange,itdidsoatgreatcost.

Eventually,itbecamecommonpracticeforthenewownerofthefeinottobothertotakephysicalpossessionofthestone.Instead,thenewowneracceptedaclaimtothefeiwithoutmovingit.Infuturebargains,hetradedthisclaimforgoodsthathewanted.Havingphysicalpossessionofthestonebecamelessimportantthanhavinglegalclaimtoit.

Thispracticewasputtoatestwhenavaluablestonewaslostatseaduringastorm.Becausetheownerlosthismoneybyaccidentratherthanthroughnegligence,everyoneagreedthathisclaimtothefeiremainedvalid.Evengenerationslater,whennoonealivehadeverseenthisstone,theclaimtothisfeiwasstillvaluedinexchange.

Moneyquantity

Thequantityofmoneyavailableiscalledthemoneysupply.

Thecontroloverthemoneysupplyiscalledmonetarypolicy.

Measureofmoney

TheQuantityTheoryofMoney

TransactionsandtheQuantityEquation

MV=PT

FromTransactionstoIncome

MV=PY

TheMoneyDemandFunctionandthequantityEquation

Realmoneybalance:

M/P

Moneydemandfunction:

（M/P）^（d）=kY

Noticethat（M/P）d=M/P,andMV=PY,therefore,V=1/k.

TheAssumptionofConstantVelocity

Quantitytheoryofmoney

Ifvelocityisfixed,thequantityofmoneydeterminesthedollarvalueoftheeconomy’soutput.

Money,Prices,andInflation

%ChangeinM+%ChangeinV=%ChangeinP+%ChangeinY.

Thequantitytheoryofmoneystatesthatthecentralbank,whichcontrolsthemoneysupply,hasultimatecontrolovertherateofinflation.Ifthecentralbankkeepsthemoneysupplystable,thepricelevelwillbestable.Ifthecentralbankincreasesthemoneysupplyrapidly,thepricelevelwillriserapidly

InflationandMoneyGrowth

“Inflationisalwaysandeverywhereamonetaryphenomenon.’’SowroteMiltonFriedman,thegreateconomistwhowontheNobelPrizeineconomicsin1976.

Thequantitytheoryofmoneyleadsustoagreethatthegrowthinthequantityofmoneyistheprimarydeterminantoftheinflationrate.YetFriedman’sclaimisempirical,nottheoretical.Toevaluatehisclaim,andtojudgetheusefulnessofourtheory,weneedtolookatdataonmoneyandprices.

Figureaboveexaminesthesamequestionwithinternationaldata.Itshowstheaveragerateofinflationandtheaveragerateofmoneygrowthinmorethan100countriesduringtheThelinkbetweenmoneygrowthandinflationclear.Countrieswithhighmoneygrowthtendtohavehighin?

ation,andcountrieswithlowmoneygrowthtendtohavelowinflation.

Seigniorage

Therevenueraisedthroughtheprintingofmoneyiscalledseigniorage.

Printmoney→moneysupplyincrease→inflation

Inflationtax

PayingfortheAmericanRevolution

AlthoughseignioragehasnotbeenamajorsourceofrevenuefortheU.S.governmentinrecenthistory,thesituationwasverydifferenttwocenturiesago.Beginningin1775theContinentalCongressneededtofindawaytofinancetheRevolution,butithadlimitedabilitytoraiserevenuethroughtaxation.It,therefore,reliedontheprintingoffiatmoneytohelppayforthewar.

TheContinentalCongress’srelianceonseigniorageincreasedovertime.In1775newissuesofcontinentalcurrencywereabout$6million.Thisamountincreasedto$19millionin1776,$13millionin1777,$63millionin1778,and$125millionin1779.

Notsurprisingly,thisrapidgrowthinthemoneysupplyledtomassiveinflation.Attheendofthewar,thepriceofgoldmeasuredincontinentaldollarswasmorethan100timesitslevelofonlyafewyearsearlier.Thelargequantityofthecontinentalcurrencymadethecontinentaldollarnearlyworthless.Thisexperiencealsogavebirthtoaonce-popularexpression:

peopleusedtosaysomethingwa