庇古税和污染许可证的等同性 The Equivalence of Pigovian Taxes and 总结 Pollution permits Summary (a)席古魂Pigo (b)洞集许可证 Pollution permits 双方间的交易直接影响到第三方,这种影响被称 When a transaction between a buver and a seller directly affects a third party, the effect is called an externality ◆负外部性导致的社会最优数量低于市场均衡数量 Negative externalities cause the socially optimal quanti in a market to be less than the equilibrium quantity ◆正外部性导致的社会最优数量高于市场均衡数量 Positive externalities cause the socially optimal quantity in a market to be greater than the equilibrium quantity of pollution. 总结 总结 Summary Summary ◆受到外部性影响的人们有时候可以私下解决 当利益各方不能充分解决外部性时,政府 问题 应该介入 Those affected by externalities can When private parties cannot adequately sometimes solve the problem privately deal with externalities, then the ◆科斯定理是说如果利益各方能够无成本地协 government steps in. 商,那么他们总会达成协议使资源配置有效 ◆政府可以进行管制,也可以通过征收庇古 税使外部性内在化 The Coase theorem states that if people can The government can either regulate bargain without a cost, then they can alway behavior or internalize the externality by reach an agreement in which resources are ing pigovian taxes. allocated efficiently10 55 庇古税和污染许可证的等同性… The Equivalence of Pigovian Taxes and Pollution Permits… 污染量 Quantity of Pollution 0 Price of Pollution 污染价格 P Q 对污染权的需求 Demand for pollution rights 庇古税 Pigovian tax (a)庇古税 Pigovian Tax 2. …它与需求 曲线一起决定了污染量。 ...which, together with the demand curve, determines the quantity of pollution. 1庇古税设 定污染价格 A Pigovian tax sets the price of pollution... 污染数量 Quantity of Pollution 0 Q 对污染权的需求 Demand for pollution rights 排污许可证的供给 Supply of pollution permits (b)污染许可证 Pollution Permits 污染 价格 Price of Pollution P 2. …它与需求 曲线一起决定了污染价格。 ...which, together with the demand curve, determines the price of pollution. 1.污染许可证 设定排污量 Pollution permits set the quantity of pollution... 56 总结 Summary ‹ 当买卖双方间的交易直接影响到第三方，这种影响被称 之为外部性。 When a transaction between a buyer and a seller directly affects a third party, the effect is called an externality. ‹ 负外部性导致的社会最优数量低于市场均衡数量。 Negative externalities cause the socially optimal quantity in a market to be less than the equilibrium quantity. ‹ 正外部性导致的社会最优数量高于市场均衡数量。 Positive externalities cause the socially optimal quantity in a market to be greater than the equilibrium quantity. 57 总结 Summary ‹ 受到外部性影响的人们有时候可以私下解决 问题。 Those affected by externalities can sometimes solve the problem privately. ‹ 科斯定理是说如果利益各方能够无成本地协 商，那么他们总会达成协议使资源配置有效 率。 The Coase theorem states that if people can bargain without a cost, then they can always reach an agreement in which resources are allocated efficiently. 58 总结 Summary ‹当利益各方不能充分解决外部性时，政府 应该介入。 When private parties cannot adequately deal with externalities, then the government steps in. ‹政府可以进行管制，也可以通过征收庇古 税使外部性内在化。 The government can either regulate behavior or internalize the externality by using Pigovian taxes