资源与环境经济学Chapter 5

Chapter 5
Sustainable Development: Defining The Concept
1. Introduction

Main 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 a fair intertemporal allocation. Take this theoretical definition and consider how it can be made operationally measurable.

Figure 5.1
2. A Two-Period Modeallocation 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 from the last unit in period 1 equals the present value of the marginal net benefit in period 2.
5. Applying The Sustainability Criterion

How do we apply Hartwick Rule to environment? In general, the Hartwick Rule suggests that the current generation has been given an endowment. Sustainable use of this endowment implies that we should keep the principal (the value of the endowment ) intact and live off only the flow of services provided.
5. Applying The Sustainability Criterion

Weak sustainability means that resource use by previous generations should not exceed a level that would prevent subsequent generations from achieving 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.
3. Defining Intertemporal Fairness

The sustainability criterion suggests that, at a minimum, future generations should be left no worse off than current generations.
2. A Two-Period Model

Assume: 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 is given by the formula P=8-0.4q, and marginal cost is constant at $2 per unit.
3. Defining Intertemporal Fairness
Do our institution provide adequate protection for future generations? Are all efficient allocations sustainable?
5. Applying The Sustainability Criterion

Two important insights flow from Hartwick’s reinterpretation of the sustainability criterion. First, with this version it is possible to judge the sustainability of an allocation by examining whether or not the value of the total capital stock is nondeclining. Second, this analysis suggests the specific degree of sharing that would be necessary to produce a sustainable outcome, namely all scarcity rent must be invested.
2. A Two-Period Model

According to dynamic efficiency, the objective is to balance present and future uses of this resource by maximizing the present value of the net benefits derived from the use of those resources. This implies a particular allocation of the resource across time.
2. A Two-Period Model


Both the size of the marginal user cost and the allocation of the resource between the two period is affecter by the discount rate. 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 relative value of present and future resource use.
4. Are Efficient Allocation Fair?

Although dynamic efficient allocations do not automatically satisfy sustainability criteria, they can be perfectly consistent with sustainability, even in an economy relying heavily on depletable resources because it will always be 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..

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 period than to the second.
2. A Two-Period Model
If the total supply were 30 or greater, what’s 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?
5. Applying The Sustainability Criterion

Is it possible to develop a version of the sustainability criterion that is more operational? Fortunately it is, thanks to what has 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 were invested in capital.