1 公共物品与共有资源 Public Goods and Common Resources 第11章 Chapter 11 2 “生活中最好的东西是免费的…” “The best things in life are free. . .” 免费物品向经济学分析提出了特别的挑战 Free goods provide a special challenge for economic analysis 经济中的大多数物品都是在市场中得以配置的 Most goods in our economy are allocated in markets… …对于这些物品，价格就是指导买者和卖者决策的 信号 …for these goods, prices are the signals that guide the decisions of buyers and sellers 3 “生活中最好的东西是免费的…” “The best things in life are free. . .” 当物品可以免费获得时，通常用以配置 资源的市场力量就难以发挥作用了。 When goods are available free of charge, the market forces that normally allocate resources in our economy are absent. 4 “生活中最好的东西是免费的…” “The best things in life are free. . .” 当一个物品没有被标价，私人市场就不 能保证该物品能在合适的数量下进行生 产和消费。 When a good does not have a price attached to it, private markets cannot ensure that the good is produced and consumed in the proper amounts. 5 “生活中最好的东西是免费的…” “The best things in life are free. . .” 在这种情况下，政府政策就有可能矫正 由此导致的市场失灵，提高经济福利。 In such cases, government policy can potentially remedy the market failure that results, and raise economic well- being. 6 物品的不同类型 The Different Kinds of Goods 当考虑经济中的不同物品时，可以将它们 按两个特征来分组： When thinking about the various goods in the economy, it is useful to group them according to two characteristics: ?该物品是排他的吗？ Is the good excludable? ?该物品是竞争的吗？ Is the good rival? 2 7 物品的不同类型 The Different Kinds of Goods ?排他性Excludability： 可以阻止其他人享用该物品 People can be prevented from enjoying the good. 8 物品的不同类型 The Different Kinds of Goods ?竞争性Rivalness： 某人对该物品的使用减少其他人对 该物品的享受。 One person’s use of the good diminishes another person’s enjoyment of it. 9 四类物品 Four Types of Goods ?私人物品Private Goods ?公共物品Public Goods ?共有资源Common Resources ?自然垄断Natural Monopolies 10 物品类型 Types of Goods ?私人物品Private Goods ?既有排他性，又有竞争性。 Are both excludable and rival. ?公共物品Public Goods ?既无排他性，又无竞争性。 Are neither excludable nor rival. 11 物品类型 Types of Goods ?共有资源Common Resources ?有竞争性，但无排他性。 Are rival but not excludable. ?自然垄断Natural Monopolies ?有排他性，但无竞争性。 Are excludable but not rival. 12 物品类型 Types of Goods 公共物品Public Goods ?国防National defense ?知识Knowledge ?不拥挤的不收费公路 Uncongested nontoll roads 共有资源Common Resources ?海洋中的鱼Fish in the ocean ?环境The environment ?拥挤的不收费公路Congested nontoll roads 自然垄断Natural Monopolies ?消防Fire protection ?有线电视Cable TV ?不拥挤的收费公路Uncongested toll roads 私人物品Private Goods ?冰淇淋蛋卷Ice-cream cones ?衣服Clothing ?拥挤的收费公路Congested toll roads 竞争Rival? 是Yes 否No 排他性 Excludable? 是Yes 否No 3 13 搭便车问题 The Free-Rider Problem 一个人从一种物品中获益，但 却逃避了为此支付，则他就是 搭便车者。 A free-rider is a person who receives the benefit of a good but avoids paying for it. 14 搭便车问题 The Free-Rider Problem ?既然人们不能被排除在对公共物品的享用之 外，个人就会拒绝为该物品支付，寄希望于 别人为此支付。 Since people cannot be excluded from enjoying the benefits of a public good, individuals may withhold paying for the good hoping that others will pay for it. ?搭便车问题阻碍了私人市场提供公共物品。 The free-rider problem prevents private markets from supplying public goods. 15 例子：宿舍打水 ?宿舍打水具有公共品的性质： ?非竞争性：使用人数（适当地）增加不影响每个人 的使用 ?非排他性：很难阻止其他人使用 ?假设宿舍有两个人，打水给每个使用者带来的 收益为2。 ?打水的总成本为3；如果两人分摊（轮流打水 ），每人成本为1.5。 16 例子：宿舍打水 (0, 0)(2, -1)逃避 (-1, 2)(0.5, 0.5)打水张三 逃避打水 李四 （张三的净收益，李四的净收益） 均衡的结果是双方都 逃避；而双方都打水 使得每个人都更好 17 解决搭便车问题 Solving the Free-Rider Problem ?政府可以决定提供公共物品，只要总收益大 于总成本。 The government can decide to provide the public good if the total benefits exceed the costs. ?通过提供公共物品，并用税收收入来为此支 付，政府能够让每个人都变得更好。 The government can make everyone better off by providing the public good and paying for it with tax revenue. 18 一些重要的公共物品 Some Important Public Goods ?国防National Defense ?基础研究Basic Research ?反贫困项目Programs to Fight Poverty 4 19 灯塔是否是公共物 品？ Are Lighthouses Public Goods? 20 成本－收益分析 Cost-Benefit Analysis ?为了判断是否要提供公共物品，必须要比较使 用该物品的所有人的总收益和提供与维护该公 共物品的各种成本。 In order to decide whether to provide a public good or not, the total benefits of all those who use the good must be compared to the costs of providing and maintaining the public good. ?成本－收益分析就是要估计物品对社会整体而 言的总成本和总收益。 Cost benefit analysis estimates the total costs and benefits of a good to society as a whole. 21 成本－收益分析 Cost-Benefit Analysis ?成本－收益分析被用来估计某一工程对社会整 体而言的总成本和总收益。 A cost-benefit analysis would be used to estimate the total costs and benefits of the project to society as a whole. ?做这件事件是困难的，因为赖以估计社会收益和资源 成本的价格并不存在。 It is difficult to do because of the absence of prices needed to estimate social benefits and resource costs. ?生命的价值、消费者的时间和审美价值都难以评估。 The value of life, the consumer’s time, and aesthetics are difficult to assess. 22 共有资源 Common Resources 共有资源，和公共物品一样，不具 有排他性。对于想使用的人，总是 可以免费得到它们。 Common resources, like public goods, are not excludable. They are available free of charge to anyone who wishes to use them. 23 共有资源 Common Resources 共有资源是具有竞争性的物品， 因为某人对共有资源的使用减少 了其他人的使用。 Common resources are rival goods because one person’s use of the common resource reduces other people’s use. 24 共有资源的例子 Examples of Common Resources ?清洁的空气和水 Clean air and water ?石油矿藏Oil pools ?拥挤的道路Congested roads ?鱼类、鲸鱼和其他野生动植物 Fish, whales, and other wildlife 5 25 共有地悲剧 Tragedy of the Commons 共有地悲剧是一个寓言，说明从整个社会的角度来看，为什 么共有资源的使用大于令人满意的水平。 The Tragedy of the Commons is a parable that illustrates why common resources get used more than is desirable from the standpoint of society as a whole. ?当某人使用了共有资源，他（她）就减少了其他人对它的享受。 When one person uses a common resource, he or she diminishes another person’s enjoyment of it. ?当个人没有因使用而付费时，共有资源容易被过度使用。 Common resources tend to be used excessively when individuals are not charged for their usage. ?这产生了负外部性。 This creates a negative externality. 26 共有地悲剧：北京的道路 数据来源[1]：2005年3月7日（周一）环保组织“自然之友”组织的志愿者活动，《北京晨报》，2005年3月8日。 数据来源[2]：2005年3月17、18日（周四、五）记者行动，《北京广播电视报》，2005年3月24日。 单位：分钟 起点终点自驾车（或出租车）地铁（加步行或公交车）自行车摩托车 翠宫饭店国贸商场110 63（加步行）63 [1] 东直门国贸商场30（出租车）29（加步行）25 22 [1] 安定门国贸商场 比开车快16分钟[1] 北京师范大学南门复兴商业城72 65（加公交车）45 [2] 路线交通方式 数据来源 北京早高峰时间的道路交通 27 共有地悲剧的解决方法 ?数量控制 ?税收 ?许可证 ?产权私有化 28 为什么奶牛没有绝种？ Why Isn’t the Cow Extinct? 私人所有权 和利润动机！ Private Ownership and the Profit Motive! 29 产权的重要性 Importance of Property Rights 当产权没能很好地被确立（或者说，某些有 价值的物品没有让拥有合法权力的所有者来 支配它），市场就不能有效率地配置资源。 The market fails to allocate resources efficiently when property rights are not well- established (i.e. some item of value does not have an owner with the legal authority to control it). 30 产权的重要性 Importance of Property Rights 当产权缺失导致了市场失灵，政 府就有可能来解决这个问题。 When the absence of property rights causes a market failure, the government can potentially solve the problem. 6 31 总结 Summary ?物品因是否具有排他性和竞争性而不同。 Goods differ in whether they are excludable and whether they are rival. ?如果有可能阻止别人使用某物品，则称该物品具有 排他性。 A good is excludable if it is possible to prevent someone from using it. ?如果某人对一物品的享用妨碍了其他人对同一物品 的享用，则称该物品具有竞争性。 A good is rival if one person’s enjoyment of the good prevents other people from enjoying the same unit of the good. 32 总结 Summary ?公共物品既无竞争性，又无排他性。 Public goods are neither rival nor excludable. ?由于人们使用公共物品不需要付费，当该物品由 私人提供时，他们就有激励去搭便车。 Because people are not charged for their use of public goods, they have an incentive to free ride when the good is provided privately. ?政府提供公共物品，而提供多少取决于成本－收 益分析。 Governments provide public goods, making quantity decisions based upon cost-benefit analysis. 33 总结 Summary ?共有资源具有竞争性，但无排他性。 Common resources are rival but not excludable. ?由于人们使用共有资源无需付费，他们就容易 过度地使用之。 Because people are not charged for their use of common resources, they tend to use them excessively. ?政府就可能会想办法限制对共有资源的使用。 Governments tend to try to limit the use of common resources.