1、Chapter 5Sustainable Development:Defining The Concept1.IntroductionMain contents:Investigate one particular fairness concern-the treatment of future generations.Begin by considering a specific,ethically challenging situation-the allocation of a depletable resource over time.Defining what we mean by
2、a fair intertemporal allocation.Take this theoretical definition and consider how it can be made operationally measurable.2.A Two-Period ModelAccording to dynamic efficiency,the objective is to balance present and future uses of this resource by maximizing the present value（现值）of the net benefits de
3、rived from the use of those resources.This implies a particular allocation of the resource across time.2.A Two-Period ModelAssume:We have a fixed supply of a depletable resource to allocate between two periods.Demand is constant in the two periods,the marginal willingness-to-pay（边际支付意愿）is given by t
4、he formula P=8-0.4q,and marginal cost（边际成本）is constant at$2 per unit.2.A Two-Period ModelIf the total supply were 30 or greater,whats the efficient allocation between two periods?If the available supply is less than 30,suppose it is equal to 20,how do we determine the efficient allocation?Figure 5.1
5、2.A Two-Period ModelHow to find the allocation that maximizes present value?The dynamically efficient allocation of this resource has to satisfy the condition that the present value of the marginal net benefit（边际净收益现值）from the last unit in period 1 equals the present value of the marginal net benefi
6、t in period 2.Figure 5.22.A Two-Period ModelAny efficient allocation method must take scarcity（稀缺）into account.Intemporal scarcity imposes an opportunity cost（机会成本）that we henceforth refer to as the marginal user cost（边际使用者成本）（边际使用者成本）.The marginal user cost is the present value of the forgone oppor
7、tunities at the margin.Figure 5.32.A Two-Period ModelAn efficient market would have to consider not only the marginal cost of extraction（边际开采成本）for this resource,but the marginal user cost（边际使用者成本）as well.In the absence of scarcity,P=MCWith the scarcity,P=MC+MUC2.A Two-Period ModelBoth the size of t
8、he marginal user cost（边际使用者成本）and the allocation of the resource between the two period is affecter by the discount rate（贴现率）（贴现率）.The general conclusion is that higher discount rates tend to skew resource extraction toward the present because they give the future less weight in balancing the relati
9、ve value of present and future resource use.3.Defining Intertemporal FairnessThe sustainability criterion（可持续（可持续标准）标准）suggests that,at a minimum,future generations should be left no worse off than current generations.3.Defining Intertemporal FairnessDo our institution provide adequate protection fo
10、r future generations?Are all efficient allocations sustainable（可持续的）?4.Are Efficient Allocation Fair?In the numerical example we have constructed,it certainly does not appear that particular efficient allocation satisfies the sustainable criterion because more resources are allocated to the first pe
11、riod than to the second.4.Are Efficient Allocation Fair?Although dynamic efficient allocations（动态有效配置）do not automatically satisfy sustainability criteria（可持续标准）,they can be perfectly consistent with sustainability,even in an economy relying heavily on depletable resources because it will always be
12、possible to set aside sufficient net benefits accrued in the first period for those in the second period,so that those in the second period will be at least as well off as they would have been with any other extraction profile.5.Applying The Sustainability CriterionOne of the difficulties in assessi
13、ng the fairness of intertemporal（跨时期的）allocations using version of the sustainability criterion is that it is so difficult to apply.5.Applying The Sustainability CriterionIs it possible to develop a version of the sustainability criterion that is more operational?Fortunately it is,thanks to what has
14、 become known as the“Hartwick Rule.”John Hartwick(1977)demonstrated that a constant level of consumption could be maintained perpetually if all the scarcity rent（稀缺租）were invested in capital.5.Applying The Sustainability CriterionTwo important insights flow from Hartwicks reinterpretation of the sus
15、tainability criterion.First,with this version it is possible to judge the sustainability（可持续性）of an allocation by examining whether or not the value of the total capital stock（总资本储备）is nondeclining.Second,this analysis suggests the specific degree of sharing that would be necessary to produce a sust
16、ainable outcome,namely all scarcity rent（稀缺租）must be invested.5.Applying The Sustainability CriterionHow do we apply Hartwick Rule to environment?In general,the Hartwick Rule suggests that the current generation has been given an endowment（资源禀赋）.Sustainable use of this endowment implies that we shou
17、ld keep the principal(the value of the endowment)intact and live off only the flow of services provided.5.Applying The Sustainability CriterionWeak sustainability（弱可持续性）（弱可持续性）means that resource use by previous generations should not exceed a level that would prevent subsequent generations from ach
18、ieving a level of well-being at least as great.One of the implications of this definition is that the value of the capital stock(natural plus physical capital)should not decline.5.Applying The Sustainability CriterionStrong sustainability（强可持续性）（强可持续性）means that the value of the remaining stock of n
19、atural capital（自然资本）should not decrease.This definition places special emphasis on preserving natural capital under the assumption that natural and physical capital offer limited substitution possibilities.5.Applying The Sustainability CriterionEnvironmental sustainability（环境的可（环境的可持续性）持续性）means tha
20、t the physical flows of individual resources should be maintained,not merely the value of the aggregate.6.Implications For Environmental PolicyIn order to be useful guides to policy,our sustainability and efficiency criteria must be neither synonymous nor incompatible.Do these criteria meet that tes
21、t?They do.Objectives&RequirementsGrasp the two-period model Understand the meaning of marginal user costUnderstand the impacts of discount rate on resource allocationUnderstand the meaning of sustainability,weak sustainability,strong sustainability and environmental sustainability Understand the rel
22、ationship between efficient allocation and fairness DiscussionCompare two versions of the two-period depletable resource model which differ only in the treatment of marginal extraction cost.Assume that in the second version the constant marginal extraction cost is lower in the second period than the
23、 first.The constant marginal extraction cost is the same in both periods in the first version and is equal to the marginal extraction cost in the first period of the second version.In a dynamic efficient allocation how would the extraction profile in the second version differ from the first?Would relatively more or less be allocated to the second period in the second version than in the first version?Would the marginal user cost be higher or lower in the second version?
