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1、Chapter 16 均衡,A market clears or is in equilibrium when the total quantity demanded by buyers exactly equals the total quantity supplied by sellers. 一、对均衡的理解,Market Equilibrium,p,D(p), S(p),q=D(p),Market demand,Market supply,q=S(p),p*,q*,D(p*) = S(p*); the market is in equilibrium.,Market Equilibriu
2、m,p,D(p), S(p),q=D(p),Market demand,Market supply,q=S(p),p*,S(p),D(p) S(p); an excess of quantity supplied over quantity demanded.,p,D(p),Market price must fall towards p*.,Market Equilibrium,p,D(p), S(p),q=D(p),Market demand,Market supply,q=S(p),p*,D(p”),D(p”) S(p”); an excess of quantity demanded
3、over quantity supplied.,p”,S(p”),Market price must rise towards p*.,Market Equilibrium,二、An example of calculating a market equilibrium when the market demand and supply curves are linear.,Market Equilibrium,p,D(p), S(p),D(p) = a-bp,Market demand,Market supply,S(p) = c+dp,p*,q*,What are the values o
4、f p* and q*?,Market Equilibrium,At the equilibrium price p*, D(p*) = S(p*). That is,which gives,and,Market Equilibrium,p,D(p), S(p),D(p) = a-bp,Market demand,Market supply,S(p) = c+dp,Market Equilibrium,三、两个特例 Two special cases are when quantity supplied is fixed, independent of the market price, an
5、d when quantity supplied is extremely sensitive to the market price.,Market Equilibrium,S(p) = c+dp, so d=0 and S(p) c.,p,q,p*,D-1(q) = (a-q)/b,Market demand,q* = c,Market quantity supplied is fixed, independent of price.,Market Equilibrium,S(p) = c+dp, so d=0 and S(p) c.,p,q,p* = (a-c)/b,D-1(q) = (
6、a-q)/b,Market demand,q* = c,p* = D-1(q*); that is, p* = (a-c)/b.,Market quantity supplied is fixed, independent of price.,供给曲线是垂直的，在这种情况下，均衡数量完全由供给曲线决定；而均衡价格完全由需求曲线决定。,Market Equilibrium,Two special cases are when quantity supplied is fixed, independent of the market price, and when quantity supplie
7、d is extremely sensitive to the market price.,Market Equilibrium,Market quantity supplied is extremely sensitive to price.,p,q,Market Equilibrium,Market quantity supplied is extremely sensitive to price.,S-1(q) = p*.,p,q,p*,D-1(q) = (a-q)/b,Market demand,q* = a-bp*,p* = D-1(q*) = (a-q*)/b so q* = a-
8、bp*,供给曲线是水平的，在这种情况下，均衡价格由供给曲线决定；而均衡数量完全由需求曲线决定。 四、比较静态分析 五、税收的影响 我们只考虑从量税,Quantity Taxes（从量税）,A quantity tax levied at a rate of $t is a tax of $t paid on each unit traded. If the tax is levied on sellers then it is called an excise tax.（货物税） If the tax is levied on buyers then it is called a sales
9、tax.（销售税）,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 actually pays the tax? How is the markets ability to generate gains-to-trade altered when paying the tax?,1.How are prices affected?,A tax makes t
10、he price paid by buyers, pb, different from the price received by sellers, ps. In fact, the buyer and seller prices must differ by exactly the amount of the tax.,Even with a tax present the market must still clear, so the quantity demanded by buyers facing the price pb and the quantity supplied by s
11、ellers facing the price ps must be equal.,and,describe the markets equilibrium. Notice that these two conditions apply no matter if the tax is levied on sellers or on buyers.,and,describe the markets equilibrium. Notice that these two conditions apply no matter if the tax is levied on sellers or on
12、buyers.,Hence, a sales tax levied at a rate of $t has exactly the same effect on a competitive markets equilibrium as an excise tax levied at a rate of $t.,p,D(p), S(p),Market demand,Market supply,p*,q*,No tax,p,D(p), S(p),Market demand,Market supply,p*,q*,An excise tax raises the market supply curv
13、e by $t, raises the buyers price and lowers the quantity traded.,$t,pb,qt,And sellers receive only ps = pb - t.,ps,p,D(p), S(p),Market demand,Market supply,p*,q*,No tax,p,D(p), S(p),Market demand,Market supply,p*,q*,An sales tax lowers the market demand curve by $t,$t,p,D(p), S(p),Market demand,Mark
14、et supply,p*,q*,An sales tax lowers the market demand curve by $t, lowers the sellers price and reduces the quantity traded.,$t,qt,ps,p,D(p), S(p),Market demand,Market supply,p*,q*,An sales tax lowers the market demand curve by $t, lowers the sellers price and reduces the quantity traded.,$t,pb,pb,q
15、t,pb,And buyers pay pb = ps + t.,ps,p,D(p), S(p),Market demand,Market supply,p*,q*,A sales tax levied at rate $t has the same effects on the markets equilibrium as does an excise tax levied at rate $t.,$t,pb,pb,qt,pb,ps,$t,2.Who actually pays the tax?,Who really pays the tax of $t per unit traded? The division of the $t between buyers and sellers is called the incidence （(税的)负担）of the tax.,p,D(p), S(p),Market demand,Market supply,p*,q*,pb,pb,qt,pb,ps,Tax paid by buyers,Tax paid by sellers,两个特例： 当供给曲线水平即具有完全弹性时，税收完全转嫁给消费者； 当供给曲线垂直即具有完全无弹性时，税收完全不转嫁给消费者。,p,数量,p*+
