北大微观经济学课件.ppt

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1、ChapterSixteenEquilibrium均衡StructureMarketequilibriumQuantitytaxandequilibriumTaxincidence（税收分担）Deadweightloss（额外净损失）MarketEquilibriumAmarketisinequilibriumwhentotalquantitydemandedbybuyersequalstotalquantitysuppliedbysellers.Alsocalled“marketiscleared”SupplymaynotequalproductionMarketEquilib

2、riumpD(p),S(p)q=D(p)MarketdemandMarketsupplyq=S(p)MarketSettingCompetitivemarketContestablemarketMarketEquilibriumpD(p),S(p)q=D(p)MarketdemandMarketsupplyq=S(p)p*q*D(p*)=S(p*);themarketisinequilibrium.MarketEquilibriumpD(p),S(p)q=D(p)MarketdemandMarketsupplyq=S(p)p*S(p’)D(p’)

3、xcessofquantitysuppliedoverquantitydemanded.p’D(p’)MarketEquilibriumpD(p),S(p)q=D(p)MarketdemandMarketsupplyq=S(p)p*S(p’)D(p’)

4、)D(p”)>S(p”);anexcessofquantitydemandedoverquantitysupplied.p”S(p”)MarketEquilibriumpD(p),S(p)q=D(p)MarketdemandMarketsupplyq=S(p)p*D(p”)D(p”)>S(p”);anexcessofquantitydemandedoverquantitysupplied.p”S(p”)Marketpricemustrisetowardsp*.MarketEquilibrium–LinearD&SAttheequilibriumpricep*,D(p*

5、)=S(p*).Thatis,whichgivesandMarketEquilibriumpD(p),S(p)D(p)=a-bpMarketdemandMarketsupplyS(p)=c+dpMarketEquilibriumCanwecalculatethemarketequilibriumusingtheinversemarketdemandandsupplycurves?Yes,itisthesamecalculation.MarketEquilibriumtheequationoftheinversemarketdemandcurve.Andtheequatio

6、noftheinversemarketsupplycurve.MarketEquilibriumqD-1(q),S-1(q)D-1(q)=(a-q)/bMarketinversedemandS-1(q)=(-c+q)/dp*q*Atequilibrium,D-1(q*)=S-1(q*).MarketinversesupplyMarketEquilibriumandAttheequilibriumquantityq*,D-1(p*)=S-1(p*).Thatis,whichgivesandMarketEquilibriumqD-1(q),S-1(q)D-1(q)=(a-

7、q)/bMarketdemandMarketsupplyS-1(q)=(-c+q)/dMarketEquilibriumTwospecialcases:quantitysuppliedisfixed,independentofthemarketprice,andquantitysuppliedisextremelysensitivetothemarketprice.MarketEquilibriumS(p)=c+dp,sod=0andS(p)ºc.pqq*=cMarketqu