曼昆微观经济学答案ch04

51Chapter4TheMarketForcesofSupplyandDemandWHAT’SNEWINTHETHIRDEDITION:Thischapterhasbeencompletelyrearrangedandrewritten.LEARNINGOBJECTIVES:Bytheendofthischapter,studentsshouldunderstand:whatacompetitivemarketis.whatdeterminesthedemandforagoodinacompetitivemarket.whatdeterminesthesupplyofagoodinacompetitivemarket.howsupplyanddemandtogethersetthepriceofagoodandthequantitysold.thekeyroleofpricesinallocatingscarceresourcesinmarketeconomies.CONTEXTANDPURPOSE:Chapter4isthefirstchapterinathree-chaptersequencethatdealswithsupplyanddemandandhowmarketswork.Chapter4showshowsupplyanddemandforagooddeterminesboththequantityproducedandthepriceatwhichthegoodsells.Chapter5willaddprecisiontothediscussionofsupplyanddemandbyaddressingtheconceptofelasticity—thesensitivityofthequantitysuppliedandquantitydemandedtochangesineconomicvariables.Chapter6willaddresstheimpactofgovernmentpoliciesonpricesandquantitiesinmarkets.ThepurposeofChapter4istoestablishthemodelofsupplyanddemand.Themodelofsupplyanddemandisthefoundationforthediscussionfortheremainderofthistext.Forthisreason,timespentstudyingtheconceptsinthischapterwillreturnbenefitstoyourstudentsthroughouttheirstudyofeconomics.Manyinstructorswouldarguethatthischapteristhemostimportantchapterinthetext.4THEMARKETFORCESOFSUPPLYANDDEMAND52Chapter4/TheMarketForcesofSupplyandDemandKEYPOINTS:1.Economistsusethemodelofsupplyanddemandtoanalyzecompetitivemarkets.Inacompetitivemarket,therearemanybuyersandsellers,eachofwhomhaslittleornoinfluenceonthemarketprice.2.Thedemandcurveshowshowthequantityofagooddemandeddependsontheprice.Accordingtothelawofdemand,asthepriceofagoodfalls,thequantitydemandedrises.Therefore,thedemandcurveslopesdownward.3.Inadditiontoprice,otherdeterminantsofhowmuchconsumerswanttobuyincludeincome,thepricesofsubstitutesandcomplements,tastes,expectations,andthenumberofbuyers.Ifoneofthesefactorschanges,thedemandcurveshifts.4.Thesupplycurveshowshowthequantityofagoodsupplieddependsontheprice.Accordingtothelawofsupply,asthepriceofagoodrises,thequantitysuppliedrises.Therefore,thesupplycurveslopesupward.5.Inadditiontoprice,otherdeterminantsofhowmuchproducerswanttosellincludeinputprices,technology,expectations,andthenumberofsellers.Ifoneofthesefactorschanges,thesupplycurveshifts.6.Theintersectionofthesupplyanddemandcurvesdeterminesthemarketequilibrium.Attheequilibriumprice,thequantitydemandedequalsthequantitysupplied.7.Thebehaviorofbuyersandsellersnaturallydrivesmarketstowardtheirequilibrium.Whenthemarketpriceisabovetheequilibriumprice,thereisasurplusofthegood,whichcausesthemarketpricetofall.Whenthemarketpriceisbelowtheequilibriumprice,thereisashortage,whichcausesthemarketpricetorise.8.Toanalyzehowanyeventinfluencesamarket,weusethesupply-and-demanddiagramtoexaminehowtheeventaffectsequilibriumpriceandquantity.Todothiswefollowthreesteps.First,wedecidewhethertheeventshiftsthesupplycurveorthedemandcurve(orboth).Second,wedecidewhichdirectionthecurveshifts.Third,wecomparethenewequilibriumwiththeinitialequilibrium.9.Inmarketeconomies,pricesarethesignalsthatguideeconomicdecisionsandtherebyallocatescarceresources.Foreverygoodintheeconomy,thepriceensuresthatsupplyanddemandareinbalance.Theequilibriumpricethendetermineshowmuchofthegoodbuyerschoosetopurchaseandhowmuchsellerschoosetoproduce.CHAPTEROUTLINE:I.MarketsandCompetitionYoumaywanttoprovidestudentswithexamplesofmarketsotherthanthetraditionalretailstoreorthestockmarket.Theseincludetheclassifiedadvertisingsectionofanewspaper,thecollege“careerservices”departmentthroughwhichtheycanlookforemploymentupongraduation,orthemarketformarijuanaonacollegecampus.Besuretolistthegoodorservicebeingsold,thebuyers,andthesellersineachexample.Chapter4/TheMarketForcesofSupplyandDemand53A.Definitionofmarket:agroupofbuyersandsellersofaparticulargoodorservice.B.Definitionofcompetitivemarket:amarketinwhichtherearemanybuyersandmanysellerssothateachhasanegligibleimpactonthemarketprice.C.Competition:PerfectandOtherwise1.Characteristicsofaperfectlycompetitivemarket:a.Thegoodsbeingofferedforsaleareallthesame.b.Thebuyersandsellersaresonumerousthatnonecaninfluencethemarketprice.2.Becausebuyersandsellersmustacceptthemarketpriceasgiven,theyareoftencalledpricetakers.3.Notallgoodsaresoldinaperfectlycompetitivemarket.a.Amarketwithonlyoneselleriscalledamonopolymarket.b.Amarketwithonlyafewsellersiscalledanoligopoly.c.Amarketwithalargenumberofsellers,eachsellingaproductthatisslightlydifferentfromitscompetitors’products,iscalledmonopolisticcompetition.D.Wewillstartbystudyingperfectcompetition.II.DemandA.TheDemandCurve:TheRelationshipbetweenPriceandQuantityDemanded1.Definitionofquantitydemanded:theamountofagoodthatbuyersarewillingandabletopurchase.2.Oneimportantdeterminantofquantitydemandedisthepriceoftheproduct.a.Quantitydemandedisnegativelyrelatedtoprice.Thisimpliesthatthedemandcurveisdownwardsloping.b.Definitionoflawofdemand:theclaimthat,otherthingsequal,thequantitydemandedofagoodfallswhenthepriceofthegoodrises.Studentsmayfindthenameforthistypeofmarketmisleading.Youwillhavetop