Chapter 7 Benefit–Cost Analysis: Benefits

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Chapter 7

Benefit–Cost Analysis: Benefits

The benefits of a good or service are equal to what people are willing to pay for it, remembering the provisos about the distribution of income and the availability of information. The marginal damage (MD) curve of the MAC–MD model shows society’s willingness to pay to reduce emissions of a pollutant and by doing so improve environmental quality.1 The MD curve is thus analogous to a demand curve for a normal good, but of course is upward-sloping because the good being measured is undesirable and our well being increases the less we have of it. Total benefits are measured as the area under the MD curve from the initial to the target level of pollution, as we have shown in Chapter 5. These are the damages forgone by the reduction in pollution/improvement in environmental quality (EQ). This chapter examines techniques for measuring this WTP to reduce pollution. The challenge is that there are no markets where people buy and sell units of environmental quality, so we can’t measure benefits directly the way we can with market goods. Indirect means must often be used. As one environmental economist has put it: “benefit estimation often involves a kind of detective work for piecing together the clues about the values individuals place on [environmental services] as they respond to other economic signals.”2

1. Remember, we are dealing with pollution emissions; the link between reductions in emissions and increases in environmental quality may be complex, as we must also know the effect of emissions on ambient environmental quality. This is especially so with accumulative pollutants. To keep things as simple as possible, we continue to link directly a reduction in emissions to an improvement in environmental quality.

2. Myrick Freeman III, “Benefits of Pollution Control in U.S. Environmental Protection Agency, Critical Review of Estimating Benefits of Air and Water Pollution Control, Washington, D.C., EPA 600/5-78-014, 1978, pp. II–16.

The measurement of benefits is an activity pursued on many levels. For an analyst working in an environmental agency, it can turn into a plug-in-the-numbers exercise. So many acres of clam bed destroyed (information provided by a marine biologist) times the going price of clams (provided by a quick trip to the local fish market) equals damages of water pollution in Howe Sound or the Bay of Fundy. In this case the market price of the good clearly reflects people’s willingness to pay for it, as was shown in Chapter 3. Market demand curves can be used to determine total benefits (the area under the demand curve) of reducing pollution. This will be equivalent to a reduction in total damages (area under the MD curve). To repeat,

the loss of a one unit of a market good due to pollution can be valued at its price because the market price represents marginal willingness to pay for the good.

Environment Canada:

U.S. Environmental Protection Agency:

At the other extreme, environmental economists deal with all sorts of environmental goods that have no market or market prices to use to measure WTP for pollution reductions/EQ improvements. Methods must be developed to measure WTP and impute the MD curve (or what is equivalent—a demand curve for EQ improvements). Thus,

valuing the loss of a non-market good due to pollution requires methods of imputing the marginal willingness to pay for damage reduction/EQ improvement because market prices do not exist.

This chapter offers a menu of different techniques for imputing or valuing WTP for reductions in pollution/improvements in EQ. There is no single approach that can be used in all cases; each has challenges in measurement and interpretation.

The techniques can be broken down into two main categories:

 Approaches that can use market prices to reflect WTP. These measure damages in the form of loss of incomes and output, reduced productivity, and expenditures needed to offset environmental damages. Another term often used is a direct approach to measurement of WTP.

 Approaches that are based on imputing willingness to pay of individuals as revealed through their behaviour or upon direct questioning. These are used when there is no actual market and hence market prices to reflect environmental values. These techniques are sometimes called indirect approaches to measuring WTP.

Table 7-1 lists these methods and gives examples of the types of environmental issues to which they are applied. We begin with economic damage approaches, focusing particularly on health.

Estimation of Economic Damages

When environmental degradation occurs, it produces damages; the emissions control model of Chapter 5 is based in part on the relationship between emissions and marginal damages—the MD function. So in a very direct sense the benefits of improved environmental quality come about because of reduced damages. To measure a complete emissions damage function, it is necessary to go through the following steps:

1. Measure emissions,

2. Determine the resulting ambient quality,

3. Estimate human exposure,

4. Measure impacts (health, aesthetic, recreation, ecosystem, etc.),

5. Estimate the values of these impacts.

Table 7-1: Valuation Methods for Benefit Estimation

The first three of the steps are largely the work of physical scientists. Models that show the relation between emissions and ambient levels are often called diffusion models. Step 4 involves economists to some extent, but also biological scientists and epidemiologists. The linkage of steps 3 and 4 is often called a dose–response function. This means estimating the response in terms, for example, of human mortality and morbidity to varying exposure levels to environmental pollutants. Step 5 is where economics comes strongly into play, in estimating the values associated with different impacts as identified in the previous step. This is generally a major challenge, as we will see in the coming sections.

Direct Estimation of Economic Damages

Health Damages

All forms of pollution can have an adverse impact on human health. For example, air pollution has long been thought to increase mortality and morbidity among people exposed to it, certainly in the episodic releases of toxic pollutants but also from long-run exposure to such pollutants as SO2 and particulate matter. Diseases such as bronchitis, emphysema, and lung cancer are thought to be traceable in part to polluted air. Estimates of the health costs of air pollution suggest that many billions of dollars are lost each year. Water pollution also produces health damages, primarily through contaminated drinking-water supplies. So the measurement of the human health damages of environmental pollution is a critical task for environmental economists.

Fundamental to this work is the underlying dose–response relationship showing the relationship between human health and exposure to environmental contaminants. Many factors affect human health—lifestyles, diet, genetic factors, age—besides ambient pollution levels. To separate out the effects of pollution, one has to account for all the other factors or else run the risk of attributing to pollution effects that are actually caused by something else. This calls for large amounts of accurate data on health factors as well as the numerous suspected causal factors. Some of this—air or water quality, mortality statistics, and so on—may be available from published sources, but these may be too highly aggregated to give accurate results. Similarly, although published data may give us information on, for example, average air-pollution levels in certain areas of a city, it doesn’t give completely accurate exposure data because that depends on how long individuals have lived in that environment. In a mobile society it is hard to develop accurate exposure data for people, since they may have lived in a variety of places throughout their lives. Epidemiologists have developed extensive experience with panel data, information developed through in-depth interviews with people about their lifestyles, consumption habits, locational history, and so on. A number of studies have been done that estimate the reduction in mortality or morbidity due to reductions in pollution. Morbidity measures look at indicators such as days absent from work or days affected by ill health. There is no general consensus on the estimates for the impacts of air or water pollution. One conclusion is that the results one gets are very sensitive to the data used and the way they are handled, which means we are still very uncertain about the exact links between air pollution and human mortality and morbidity rates.

The main work of economists comes after the dose–response research, in putting values on the various health impacts. How should we approach placing a value on a life prematurely shortened or on a debilitating illness suffered as a result of exposure to environmental pollutants? Your first reaction may be that it’s a dubious moral exercise to try to attach a monetary value to a human life. Isn’t life “priceless”? In a sense it is. If you stop a person in the street and ask her how much her life is worth, you may not get an answer because the question seems to violate a common moral standard. Nevertheless, society as a whole—that is, all of us acting collectively—doesn’t behave that way. In fact, through our collective decisions and behaviour, we implicitly assign values to human lives. The clearest place to see this is in traffic control. Each year, thousands of people are killed on the nation’s highways. Yet we do not see a massive outpouring of funds to redesign highways, slow traffic, or make substantially safer cars. This is because we are making an implicit trade-off between traffic deaths and other travel-related impacts, especially the benefits of reasonably fast and convenient travel. The same may be said of other risky technologies and practices we see frequently. Thus, it makes sense to examine the values that society actually places on lives and human health in the everyday course of its operation.

For some years it was standard procedure to estimate health damages by looking at such things as

 reductions in worker productivity accompanying deteriorated health and shortened lives that reduces their human capital; and

 increased monetary expenditures on health care.

For example, we might try to measure the value of a human life by looking at the economic contribution that society forgoes when that life is stopped. Over their working lives, people contribute to the production of useful goods and services enjoyed by others in society. When they die, this productivity ceases; thus, we might estimate the cumulative value of production that they would have produced had they lived. Lost productivity would vary among individuals as a function of their age, skills, and employment history, so we might take averages for people in different categories. Disease or disability caused by pollution also reduces one’s human capital and, hence, lifetime earnings capacity. For example, children suffering neurological damage from lead (from leaded gasoline, paint) or mercury (contaminated fish, mercury in water) in the environment will not be able to realize the intellectual potential they would have had in a cleaner environment. These approaches are commonly used, but of course only capture the economic contributions a person makes, not their role in their families and community, and non-economic aspects important to society.

Another approach used to measure health damages is medical expenditures. As health is affected by increasing pollution we would expect increased medical expenditures on things like hospitals, doctors, and rehabilitation. Reducing pollution would, therefore, lead to a reduction in medical expenditures, which can be counted as a benefit of the environmental change.

Output Losses and Materials Damage

Air pollution can reduce crop yields on exposed farms; it can also reduce the growth rates of commercially valuable timber. Water pollution can adversely affect firms and municipalities that use the water for production purposes or for domestic use. Diminished water quality can also have a negative impact on commercial fishing industries. Soil contamination can have serious impacts on agricultural production. Pollution in the workplace can reduce workers’ effectiveness and can often increase the rate at which machinery and buildings deteriorate. In these cases the effects of pollution are felt on the production of goods and services. The damage caused by the pollution comes about because it interferes in some way with these production processes, in effect making it more costly to produce these outputs than it would be in a less polluted world. How we actually measure production-related benefits of reducing pollution depends on circumstances.

Example: Increases in agricultural output due to pollution reductions

A small group of agricultural producers in B.C.’s Fraser Valley are affected by airborne emissions coming from an upwind factory. Pollutants from the factory have depressed crop yields, so reducing emissions will cause yields to increase. The crop being produced is sold in a national market, and its price will be unaffected by the output changes in this one region. This situation is depicted in Figure 7-1. In this diagram, S1 (=MC1) is the supply curve (marginal costs) for this group of farms before the improved air quality; S2 (=MC2) is the supply curve (marginal cost) after the improvement. Price of the output is p1. Before the change, these farmers produce at an output level of q1, while after the improvement their output increases to q2.

Figure 7-1: Benefits from Reduced Production Costs

Benefits from reduced production costs due to better environmental quality are shown with a shift of the supply curve from S1 to S2. The value of the increase in output from q1 to q2 is area d plus e. If farmers also change their input mix, the total benefits can be estimated as the improvement in net income due to the change in environmental quality. This is area (a + b + d) minus area a, which equals area (b + d). This is called the change in producer surplus.

One way of approximating the benefits of this environmental improvement is to measure the value of increased output produced by this group of farms. The increased output is simply multiplied by the price of the crop. This gives an estimate corresponding to the area (d + e) in Figure 7-1.

But the value of the increase in output is not consistent with the notion underlying our models that it is the WTP for this environmental quality improvement that matters. The problem with taking just the value of the increased output is that it is not the net benefit to the farmer and hence does not measure WTP. Net benefits are their net incomes.3 Production costs may also have changed and these must be netted out. When air pollution diminishes, farmers may actually increase their use of certain inputs and farm this land more intensively. How do we account for this possibility?

3. In this example net income is also equal to operating profits (total revenues minus variable costs) because there are no fixed costs of production.

The full change can be analyzed as follows, using net incomes of the farmers (total value of output minus total production costs).

Computation of net income:

Situation before the change:

Total value of output: a + b + c

Total costs: b + c

Net income: a

Situation after the change:

Total value of output: a + b + c + d + e

Total costs: c + e

Net income: a + b + d

Thus, the improvement in net incomes is (a + b + d) – a, or an amount equal to area (b + d) in Figure 7-1. The area above the supply curve and below the market price of the good summed over all units produced (i.e., from zero to q1 or q2) is called producer surplus. Producer surplus represents net income (net benefits) to producers. With a uniform market price and rising marginal costs (as represented by the rising supply curve), producers have net income greater than zero for all units produced up until the last unit (q1 or q2), where price is exactly equal to marginal cost in a competitive industry. The improvement in net income from the reduction in production costs is thus the net change in producer surplus from production: at q1 to q2 this is area b + d. This is the maximum the farmer would be willing to pay to reduce pollution and hence can be seen as her total benefit from reducing pollution damages (area under the MD curve).

It is often difficult to obtain the data needed to estimate supply curves, but note that information on operating profits may be easier to obtain. However, many studies measure changes in output, rather than changes in producer surplus (net income to producers). A number of studies have been done along these lines.4 Moskowitz et al.5 studied the effects of air pollution on alfalfa in the United States. They measured the quantity of production lost because of air pollution and valued this loss at the going price of alfalfa. They found that air pollution was responsible for a loss in 1974 of between $24-million and $210-million. The difference between these figures comes about because of uncertainties over the actual pollution dose the alfalfa received in that year. Another study was done by Page et al.6 to measure crop-related air-pollution losses in a six-state area. They estimated annual losses in the production of soybeans, wheat, and corn and then aggregated these to see what the present value of total losses would be over the period 1976–2000. They came up with an estimate of about $7-billion. However, these may be underestimates of the annual damages to crops. A recent study done for NASA in the United States, estimated the impact of ozone on soybean crops alone was $2 billion annually. New Footnote #1

4.These studies are reviewed in Gardner M. Brown, Jr., and Mark L. Plummer, “Market Measures of User Benefits,” in Acid Deposition: State of Science and Technology, Report 27, Methods for Valuing Acidic Deposition and Air Pollution Effects (Washington, D.C., U.S. Superintendent of Documents: National Acid Precipitation Assessment Program, 1990) 27–35 to 27–73.

5. Paul D. Moskowitz et al., “Oxidant Air Pollution: A Model for Estimating Effects on U.S. Vegetation,” Journal of Air Pollution Control Association 32(2) (February 1982): 155–160.

6. Walter P. Page et al., “Estimation of Economic Losses to the Agricultural Sector from Airborne Residuals in the Ohio River Basin,” Journal of Air Pollution Control Association, 32(2) (February 1982): 151–154.

New Footnote #1: NASA “Satellite Measurements Help Reveal Ozone Damage to Important Crops”, May 25, 2009, accessed at:, August 31, 2010.

Air Quality Ontario: www.airquality

Several Canadian studies have been done on the effects of ground-level ozone on crops.7 Ozone is seen as the most damaging air pollutant to crops in Canada, impairing the growth and yields of sensitive plants. The value of reduced crop yields per year in southern Ontario ranges from $17-million to $70-million, depending on the year chosen. The reason the range is so large is that the number of severe ozone days varies per year. Lost production in the Fraser Valley of B.C. is estimated at $8.8-million annually.

7.These studies are cited in Environment Canada, Ground-Level Ozone in Canada, A State of the Environment Fact Sheet, No. 92-1, Catalogue No. EN1-12/92-1E (Ottawa: Ministry of Supply and Services, 1992), 4.

Air pollutants cause damage to exposed surfaces, metal surfaces of machinery, stone surfaces of buildings and statuary, and painted surfaces of all types of items. The most heavily implicated pollutants are the sulphur compounds, particulate matter, oxidants, and nitrogen oxides. For the most part, the damage is from increased deterioration that must be offset by increased maintenance and earlier replacement. In the case of outdoor sculpture, the damage is to the aesthetic qualities of the objects.

In this case the dose–response relationship shows the extent of deterioration associated with exposure to varying amounts of air pollutants. The basic physical relationships may be investigated in the laboratory, but in application to any particular area one must have data on the various amounts of exposed materials that actually exist in the study region. Then it is possible to estimate the total amount of materials deterioration that would occur in an average year of exposure to the air of the region with its “normal” loading of various pollutants. One must then put a value on this deterioration. Taking a strict damage-function approach, we could estimate the increased cost of maintenance (labour, paint) made necessary by this deterioration.8

8. This approach is taken from R. L. Horst et al., A Damage Function Assessment of Building Materials: The Impact of Acid Deposition (Washington, D.C.: U.S. Environmental Protection Agency, 1986).

Problems with Direct Damage Measures

The benefit of using direct damage estimates is that they take advantage of market prices for valuation. The basic problem is that they are almost always seriously incomplete and underestimate total damages. Consider the case of measuring health damages by lost productivity and medical expenditures. They measure the value of marketed goods and services a person might, on average, produce. So the many non-market contributions people make, both inside and outside the home, don’t get counted. This method would also assign a zero value to anyone unable to work, or a retiree. There is also the question of whether a person’s consumption should be subtracted from his production to measure his actual net contribution. This might seem reasonable, but it leads to awkward conclusions—such as the premature death of a welfare recipient would be a benefit to society. There are numerous monetary, as well as psychic, benefits received by others—friends and relatives, for example—that the productivity measure does not account for. Nor does it account for the pain and suffering of illness. Thus, although the productivity-study approach may be useful in some circumstances, it can give misleading results in others because it does not fully reflect willingness to pay in its broadest context.

The same may be said of using medical expenditures to estimate damages from reduced environmental quality. For example, an asthma attack due to urban smog may cost a woman $300 per day for asthma drugs and hospital treatment costs for each severe attack. While $300 per person per high-smog day multiplied by all the asthma sufferers could amount to a lot of damage, it would no doubt be a serious understatement of the true damages of the smog-induced asthma. If the asthma sufferer were asked how much she would be willing to pay to avoid the attack or how much she would need to be compensated when she has the attack, the answer is likely to be more than the cost of medical treatment. Similarly, materials damage estimates do not take into account aesthetic losses; crop reductions do not measure damage to species diversity or broad ecosystem values. The key point is that

direct measures typically do not fully reflect the person’s WTP for EQ improvements.

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