微经课堂笔记Word文档格式.docx
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（林歆夫，2004）
注：
最佳选择即个人在约束条件下追求利益最大化。
Chapter1BasicElementsofSupplyandDemand
A.TheDemandSchedule/Curve需求曲线
Thedemandscheduleorcurveordemanddenotestherelationshipbetweenpriceandquantitydemanded,otherthingsbeingconstant.
Lawofdownward-sloppingdemand:
whenthepriceofacommodityisraised,buyerstendtobuylessofthecommodity,inotherwords,thepriceandquantityareinverselyrelated,otherthingsheldconstant.
PDD'
AA'
B
Q
BehindtheDemandCurve
Factorsaffectingthedemandcurve
1.Averageincome
2.Population
3.Priceofrelatedgoods（substitutes/complements）
4.TastesorPreference
5.Specialinfluence
当研究某一因素对需求曲线的影响时，其他因素假定不变。
AChangeinDemandandQuantityDemanded:
Anincreaseindemand:
arightwardshiftinthedemandcurve（D—D'
）oranincreaseattheamountdemandedateachprice;
Anincreaseinquantitydemanded:
movingtothedifferentpointonthesamedemandcurveafterachange（A—B）
B.TheSupplySchedule
Thesupplyscheduleorcurveorsupplydenotestherelationshipbetweenthepriceandthequantitythatproducersarewillingtoproduce,otherthingsbeingconstant.
Whenthepriceofacommodityisraised,producerstendtoproducemoreofthecommodity,inotherwords,thepriceandquantityarepositiverelated,otherthingsbeingconstant.
PSS'
Q1Q2Q
BehindtheSupplyCurve
Factorsaffectingthesupplycurve
1.Thecostofproduction
（1）thepricesofinputs
（2）Technologicaladvances
2.Pricesofsubstitutes
3.Governmentpolicy
4.Specialinfluence（Eg.weather）
Achangeinsupplyandquantitysupplied
Anincreaseinsupply:
arightwardshiftinthesupplycurve（S—S'
）oranincreaseattheamountsuppliedateachprice;
Anincreaseinquantitysupplied:
movingtoadifferentpointonthesamesupplycurveafterapricechange（A—B）.
C.Equilibriumofsupplyanddemand
Marketequilibriumorequilibriumofsupplyanddemandmeansthat:
（1）thedifferentforces（supplyanddemand）areinbalanceandtherearenoshortagesorsurpluses;
（2）theresultingprice（Pe）andquantity（Qe）alignthedesiresofpurchasersandsuppliers;
（3）thereisnotendencyforprice（Pe）toriseorfall,otherthingsbeingconstant.
Equilibriumwithsupplyanddemandcurves:
PSurplus
P2
PeE
P1Shortage
Qe
Effectofashiftinsupplyordemand
Aspellofbadweatherraisesthepriceofwheat（aningredientofbread）.SoSshiftstoS'
andashortagewilldevelopattheoriginalprice（Pe）.Thepriceofbreadthereforerises,encouragingproductionwhilediscouragingconsumption,untilquantitieswillinglybroughtandsoldareequal（E'
）.
PS'
E'
S
E
Pe
Thereisanincreaseinaverageincomes,soDshiftstoD'
andashortagewilldevelopattheoriginalprice（Pe）.Similarly,pointEshiftstoE'
.
PeShortage
InterpretingChangesintheEquilibriumPriceandQuantity
（1）Interpretinganincreaseintheequilibriumquantity
D
PS
Qe'
（2）InterpretinganIncreaseintheEquilibriumPrice
DS
P
Pe'
Pe
Chapter2ApplicationsofSupplyandDemand
A.ElasticityofDemandandSupply
Priceelasticityofdemand
Thepriceelasticityofdemandmeasureshowmuchthequantitydemandedchangeswhenitspricechanges.
=
（取正数）
ThesizeofPriceElasticityforIndividualGoods
Elasticity（
>
1）Inelasticity（
<
1）
LuxuriesNecessaries
Havereadysubstitutesinthelonghavenosubstitutesintheshortrun
run
CalculatingElasticities
（1）thePriceElasticityinanArc:
=－
PD:
Q=Q（P）
A
（2）FunctionofthePriceElasticityandthePriceElasticityatapoint
E（P）=
PriceElasticityinDigram
b/kA
b/2k
M
O
Assumeademandfunctionis:
Q（P）=－k·
P+b,k,b>
0,thefunctionofthepriceelasticityis:
E（P）=
（1）Whenthepricesdecreases（A—M）,E（P）decreases;
（2）Whenthepriceequalsb/2k（atthepointM）,thereisE（b/2k）=1（unit—elastic单位弹性）;
（3）Whenthepriceislargerthanb/2k（abovepointM）,thereisE（P）>
1（elastic）;
（4）Whenthepriceissmallerthanb/2k（belowpointM）,thereisE（P）<
1（inelastic）.
AssumeademandfunctionisQ=Q（P）,thefunctionofrevenueisR（P）=P·
R（P）
R'
（P）=Q+P·
Q'
（P）=Q·
[1+
·
（P）]=Q·
（1－E）
1.Whendemandisinelastic（E<
1）,becausethereisR'
（P）>
0,apricedecreasereducesrevenue.
2.Whendemandiselastic（E>
（P）<
0,apricedecreaseincreasesrevenue.
TheParadoxoftheBumperHarvest丰收悖论
Theparadoxofthebumperharvestdenotesthebumpercrophasloweredfarmers'
revenues.Thereasonisthatthedemandoffoodisinelastic,solargeharveststendtobeassociatedwithlowrevenues.
PriceElasticityofSupply
Thepriceelasticityofsupplymeasureshowmuchthequantitysuppliedchangeswhenitspricechanges.
D.Applicationtocurrenteconomicissues
Theeconomicsofagriculture
Someimportanttechnologicaladvancesinagriculturehaveincreasessupplygreatly（S–S'
）.Sofarmpricestendtofall（P1-P2）.Moreover,withprice-inelasticdemand,farmrevenuesdecline.（OQEP1-OQE'
P2）
D
E
P2
O
Impactofataxonpriceandquantity赋税归宿
1.Impactofataxondemandandsupply:
Ataxhasnoimpactondemand.ThesupplycurveshiftsupwardbyTafterraiseatax（thesupplydecreases）.
2.Calculatingtheincidentofatax:
taxshiftingtoconsumers:
PE'
→PE
taxshiftingtoproducers:
PE→PS
3.Impactofataxonquantityandprice
Ingeneral,thequantitydecreases（QE→QE'
）,thepriceconsumerspayoffincreases（PE→PE'
）;
thenetpriceproducersreceivedecreases（PE→PS）；
4.Generalrulesontaxshifting:
Generally,theincidenceofataxdependsupontherelativeelasticitiesofdemandandsupply.
Ataxisshiftingtoforwardtoconsumersifthedemandisinelasticrelativetosupply:
ataxisshiftedbackwardtoproducersifsupplyisrelativelymoreinelasticthandemand.
Minimumfloorsandmaximumceilings最低下限和最高上限
TheMinimum-WageControversy最低工资争论
W
_
Settingtheminimum-wageflooratW,employmentisreduced（Qe→Qm）,andunemploymentincreases（0→Qn→Qm）.
EnergyPriceControl
E’
Whenthegovernmentlegislatesamaximumpriceceiling（PE'
）,theshortageoccurs（QE→QA）andisoftenmanagedbymakingpeoplewaitinline,sothereisgreatwasteaspeoplespendvaluabletimetryingtosecuretheirneeds.
Chapter3DemandAndConsumerBehavior
UtilityTheory效用理论（这是消费者理论的基础）
Utilitydenotessatisfactionorhowconsumersrankdifferentbundleofconsumptiongoods,anditindicatesconsumerpreference.
注:
经济学所说的边际，就是数学中的导数。
Marginalutilitydenotestheadditionalutilityarisingfromconsumptionanadditionalunitofacommodity.
Q
U（Q）
MU=U’（Q）
1
4
-
2
7
3
9
10
Thelawofdiminishingmarginalutilitydenotesthemarginalutilityofthatgoodstendstodiminishastheamountofagoodconsumedincreases.（以喝水为例）
TheIndifferenceCurve（无差异曲线）
Clothing
C
U3
B
U2
U1
1.Thepoints（A,B,……）ontheindifferencecurve（U1）representconsumptionbundlesamongwhichtheconsumerpreferenceisindifferent.
2.Asweincreasebothgoodsandthusmoveinanortheasterlydirectionacrossthemap,wearecrossingsuccessiveindifferencecurves；
hence,wearereachinghigherandhigherlevelofutility.
3.Indifferencecurveareconvextotheoriginproperty（凸向原点）iscalledthelawofsubstitution.替代规律
（1）Marginalratesofsubstitution（MRS）边际替代率equaltheabsoluteslopeoftheindifferencecurve.
△F→0
MRSFC=-lim⊿c/⊿F=-dC/dF
（2）MRSarethemeasureofthegoods'
relativemarginalutilities:
U1=U（F,C）
0=ə’U/əF·
dF+əU/əC·
dC→
=MUF/MUC
MRSFC=
（3）Thelawofsubstitution（thelawofdiminishingmarginalratesofsubstitution）denotesitsMRSdiminishingasmoreandmoreofagood（F）isconsumed（A→B）.
ConsumerEquilibrium消费者平衡
BudgetLine预算线
I/PF
Assumetheconsumer'
sincomeisI,thepriceoffoodisPFandtheclothingisPC.MNistheconsumer'
sbudgetline.Itsumsupallthepossiblecombinationsofthetwogoodsthatwouldexhausttheconsumer'
sincome.ItsabsoluteslopeequalsthePF/PCratio.
TheEquilibriumPositionofTangency（tan）切点的均衡位置
PF/PC=MRSFC=MUF/MUC
N
B’
Assumetheutilityfunctionis:
U=U（F,C）,thebudgetlineis:
PF·
F+PC·
C=I.
1.GeometricalAnalysisofConsumerEquilibrium
TheconsumerisfreetomoveanywherealongthebudgetlineNM.Hewillmovetothatpoint（B）whichyieldsthegreatestutility.Geometrically,theconsumerisatequilibriumwheretheslopeofthebudgetline（=PF/PC）equalstheMRSFC（=MUF/MUC）:
PF/PC=MUF/MUC
2.MathematicalAnalysisofConsumerEquilibrium
S.t:
C=I
theLagrangefunction（拉格朗日函数）:
L（F,C,λ）=U（F,C）+λ（PF·
C-I）istheLagrangemultiplier（拉格朗日常数）
L'
F=MUF+λPF=0
C=MUC+λPC=0
λ=PF·
C-I=0
MUF/PF=MUC/PC=…=MU/P=K（constant常数）
3.Equi-marginalPrinciple:
MUF/PF=MUC/PC
Thefundamentalconditionofmaximumutilityistheequimarginalprinciple.Itstatesthataconsumerhavingafixedincomeandfacinggivenmarketpricesofgoodswillachievemaximumutilitywhenthemarginalutilityofthelastdollarspentoneachgoodisexactlyassameasthemarginalutilityofthelastdollarspentonanyothergoods.
4.WhyDemandCurveSlopesDownward
Ingeneral,weholdthemarginalutilityperdollarconstant.Therefore,accordingtotheequimarginalprinciple,ahigherpriceforagood
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