清华大学中级微观经济学讲义(清华 李稻葵)16.ppt

1、 Sixteen,Equilibrium,What Do We Do in This Chapter?,We study the concept of equilibrium We will study external changes to equilibrium,Market Equilibrium,A market is in equilibrium when total quantity demanded by buyers equals total quantity supplied by sellers.,Market Equilibrium,p,D(p), S(p),q=D(p)

2、,Marketdemand,Marketsupply,q=S(p),p*,q*,D(p*) = S(p*); the marketis in equilibrium.,Market Equilibrium,Two special cases: quantity supplied is fixed, independent of the market price, and quantity supplied is extremely sensitive to the market price.,Market Equilibrium,S(p) = c+dp, so d=0 and S(p) c.,

3、p,q,q* = c,D-1(q) = (a-q)/b,Marketdemand,Market quantity supplied isfixed, independent of price.,Market Equilibrium,Market quantity supplied isextremely sensitive to price.,S-1(q) = p*.,p,q,p*,D-1(q) = (a-q)/b,Marketdemand,Quantity Taxes,A quantity tax levied at a rate of $t is a tax of $t paid on e

4、ach unit traded. If the tax is levied on sellers then it is an excise tax. If the tax is levied on buyers then it is a sales tax.,Quantity Taxes,What is the effect of a quantity tax on a markets equilibrium? How are prices affected? How is the quantity traded affected? Who pays the tax? How are gain

5、s-to-trade altered?,Quantity Taxes,A tax rate t makes the price paid by buyers, pb, higher by t from the price received by sellers, ps.,Quantity Taxes,Even with a tax the market must clear. I.e. quantity demanded by buyers at price pb must equal quantity supplied by sellers at price ps.,Quantity Tax

6、es,and,describe the markets equilibrium.Notice these conditions apply nomatter if the tax is levied on sellers or onbuyers.,Quantity Taxes,and,describe the markets equilibrium.Notice that these two conditions apply nomatter if the tax is levied on sellers or onbuyers.,Hence, a sales tax rate $t has

7、thesame effect as an excise tax rate $t.,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,No tax,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,An excise tax raises the marketsupply curve by $t,Quantity Taxes & Market Equilibrium,p

8、,D(p), S(p),Marketdemand,Marketsupply,p*,q*,An excise tax raises the marketsupply curve by $t,raises the buyersprice and lowers thequantity traded.,$t,pb,qt,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,An excise tax raises the marketsupply curve by $t,raises the b

9、uyersprice and lowers thequantity traded.,$t,pb,qt,And sellers receive only ps = pb - t.,ps,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,An sales tax lowersthe market demandcurve by $t,$t,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p

10、*,q*,An sales tax lowersthe market demandcurve by $t, lowersthe sellers price andreduces the quantitytraded.,$t,qt,ps,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,An sales tax lowersthe market demandcurve by $t, lowersthe sellers price andreduces the quantitytrade

11、d.,$t,pb,pb,qt,pb,And buyers pay pb = ps + t.,ps,Quantity Taxes & Market Equilibrium,Who pays the tax of $t per unit traded? The division of the $t between buyers and sellers is the incidence of the tax.,Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,pb,pb,qt,pb,ps,

12、Quantity Taxes & Market Equilibrium,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,pb,pb,qt,pb,ps,Tax paid by buyers,Tax paid by sellers,Quantity Taxes & Market Equilibrium,E.g. suppose the market demand and supply curves are linear.,Quantity Taxes & Market Equilibrium,and,With the tax, the market equ

13、ilibrium satisfies,and,so,and,Substituting for pb gives,Quantity Taxes & Market Equilibrium,and,give,The quantity traded at equilibrium is,Quantity Taxes & Market Equilibrium,As t increases, ps falls, pb rises, andqt falls.,Quantity Taxes & Market Equilibrium,The tax paid per unit by the buyer is,Th

14、e tax paid per unit by the seller is,Quantity Taxes & Market Equilibrium,The total tax paid (by buyers and sellerscombined) is,Tax Incidence and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,pb,qt,ps,Tax Incidence and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsu

15、pply,p*,q*,$t,pb,qt,ps,Change to buyersprice is pb - p*. Change to quantitydemanded is Dq.,Dq,Tax Incidence and Own-Price Elasticities,Around p = p* the own-price elasticityof demand is approximately,Tax Incidence and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,pb,qt,ps,Ch

16、ange to sellersprice is ps - p*. Change to quantitydemanded is Dq.,Dq,Tax Incidence and Own-Price Elasticities,Around p = p* the own-price elasticityof supply is approximately,Tax Incidence and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,pb,pb,qt,pb,ps,Tax paid by buyers,Tax

17、paid by sellers,Tax incidence =,Tax Incidence and Own-Price Elasticities,Tax incidence =,So,Tax Incidence and Own-Price Elasticities,Tax incidence is,The fraction of a $t quantity tax paidby buyers rises as supply becomes moreown-price elastic or as demand becomesless own-price elastic.,Tax Incidenc

18、e and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,ps= p*,$t,pb,qt = q*,As market demandbecomes less own- price elastic, tax incidence shifts moreto the buyers.,When eD = 0, buyers pay the entire tax, even though it is levied on the sellers.,Deadweight Loss and Own-Price Elasticitie

19、s,A quantity tax imposed on a competitive market reduces the quantity traded and so reduces gains-to-trade (i.e. the sum of Consumers and Producers Surpluses). The lost total surplus is the taxs deadweight loss, or excess burden.,Deadweight Loss and Own-Price Elasticities,p,D(p), S(p),Marketdemand,M

20、arketsupply,p*,q*,No tax,Deadweight Loss and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,No tax,CS,PS,Deadweight Loss and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,pb,qt,ps,CS,PS,The tax reducesboth CS and PS,transfers surplusto government,Tax,Deadweight Loss and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,pb,qt,ps,CS,PS,Tax,Deadweight loss,Deadweight Loss and Own-Price Elasticities,p,D(p), S(p),Marketdemand,Marketsupply,p*,q*,$t,pb,qt,ps,Deadweight loss falls as market demand becomes less own- price elastic