CHAPTER 6

Measures and Indicators of Sustainability

Introduction

So far, we have discussed a number of conceptual issues of sustainable development and indicated some of the ambiguities and complexities that characterize the process. It is important that, despite these ambiguities and complexities, we should be able to find some indicators and measures that at least help us understand whether a community or a country or the entire world is moving in the right direction. Obviously, these indicators and measures must go beyond measuring the purely economic and be able to capture social and environmental aspects too. Broadly speaking, there are two different ways of looking at these indicators. The first approach is to look at it in terms of macro measures, such as green measures of gross domestic product or genuine savings, which will be elaborated upon later, that could be used for a country or aggregated across an entire planet. Alongside these macro measures, there are a number of micro indicators that look at more detailed aspects of human nature interactions, looking at specific localized phenomena such as air pollution in a particular suburb in a city or the reduction of available groundwater in a well in a village. Alternatively, there is another set of measures that examine the adequacy or otherwise of the supply of natural resources to support a set of life-support activities for a particular species, referred to as the carrying capacity of the ecosystem. In a similar fashion, the impact on the environment of anthropogenic activities is often measured in terms of ecological footprint, which could be for a single individual, a specific economic activity or aggregated across a community of humans. Ecological footprint is a good indicator of the demand made by human activity on the natural resources, and hence reflects the stress created on the ecosystem. It also represents the choices humankind makes about consumption and lifestyles. Therefore, it is, relatively speaking, easier to take conscious decisions about ecological footprints. Box 6.1 discusses the extent to which the ecosystem is under pressure from high per capita energy use and its implications.

Box 6.1 Projected energy stress on Mother Earth as an outcome of development: The challenge ahead

In this chapter, we start by looking at the carrying capacity, followed by ecological footprint. The interaction of the supply of and demand for ecosystem services is captured in a concept called ecological overshoot, which is discussed next. We then talk of an alternate approach, where different economic, social, and ecological indicators are analyzed to understand the state of the earth. Depending on the sustainability objective, composite indicators can be developed. To conclude, we review a proposed framework for developing sets of sustainable development indicators proposed by an OECD taskforce.

Measuring Sustainability from the Supply Side: Carrying Capacity

An obvious question that must have crossed the reader’s mind is whether there are too many people on our planet. This is especially true when we encounter crowded cities and congested roads. Even when not thinking of people, many might have wondered whether there was too much crowding inside a small pond or lake with many fish, amphibians, and water-plants, all depending on the resources available in the confines of the water body. A little reflection would tell us that there must be some physical maximum that the ecosystem of the pond can sustain. It could be the other way round too. One could think of an ecosystem where there was an abundance of resources that could accommodate more living beings within that system. In nature, very often, animals and even plants migrate to ecosystems with better resources if possible. The concept used by ecologists is that of carrying capacity of an ecosystem. It is formally defined as the population of a given species that can be supported indefinitely in a defined habitat, without permanently damaging the ecosystem upon which it is dependent (Arrow et al. 1996) (see Figure 6.1). Box 6.2 illustrates the carrying capacity as well as ecological footprints of select countries to demonstrate the wide variation across nations worldwide.

There are some problems with this particular definition. Ecosystems starting from very small localized ones to the entire earth cannot survive with one species alone. Nature, in this sense, is fundamentally interdependent. Hence, defining the carrying capacity in terms of one species can suppress the impact of this particular species on other species that share the ecosystem. It is particularly inadequate for human beings because we can access distant ecosystems in different parts of the world with the help of technology and trade. We are not limited to consuming what is available in the local ecosystem we inhabit. Therefore, for human beings, the only meaningful measure of carrying capacity must be for the entire planet because it constitutes the ultimate boundary. Hence, human carrying capacity can be redefined as the maximum rate of resource consumption and waste discharge that can be sustained without impairing the functional integrity and productivity of the planet as an ecosystem with all its other forms of living species. Even in this definition, there could be problems with the accuracy of estimates due to the fact that technological change can increase the carrying capacity (the same plot of land can now grow more food than a hundred years ago) or consumption patterns and lifestyles may change (we may decide to consume less or waste less) (Arrow et al. 2004). Similarly, excess pollution could result in a decline in the carrying capacity of the earth. At this stage, the reader would be keen on knowing whether, with increased awareness and action, there has been an improvement of bio-capacity globally. Box 6.3 discusses these trends.

Figure 6.1 Concept of carrying capacity

Box 6.2 Biocapacity: debtors and creditors

Box 6.3 Trends in biocapacity

It is little wonder that people who have made actual estimates of the carrying capacity have varied very widely in the numbers they have come up with. The estimates depend on assumptions made about technology and lifestyle changes. A lower standard of living for human beings (lower dependence on energy using technologies to save labor) would automatically result in a higher carrying capacity. The most conservative estimate has been two-three billion people, while the most liberal has been 1,000 billion people (Cohen 1997).

The largest number of estimates hover around 8 to 16 billion people. How exactly does one measure the carrying capacity? There are different estimation methods. A relatively easy way of doing it is to focus on one limiting factor, for instance, limiting food supply and its growth, and then estimating the maximum population that can be supported by the supply of food. Even in this method, there could be problems as to what could be considered as the minimal food requirements for a person, because it would vary considerably by age, health, gender, and social circumstance. In a similar vein, should we consider the absolute minimum food for survival for each person or would food be considered to be something more than a mere need for biological survival? A more sophisticated approach could be taking a set of limiting factors, such as food, water, and fuel supplies, and then trying to compute the carrying capacity. A little reflection will reveal that many of these limiting factors are actually interacting constraints. For instance, the availability of food is contingent on the use of fertilizers, which, in turn, could be constrained by the supply of fuel. On the other hand, the availability of a substitute for fuel could change the nature of the constraints substantially. Hence, the most sophisticated approach to measure biocapacity would be through a dynamic system of interactive constraints. It is imperative that estimating the upper limit of human population allows more room for interactive complexity and underlying uncertainties. Some well-known studies of dynamic systems (Forrester 1971; Meadows et al. 1972) have found that, under certain assumptions of technology and consumption patterns, the earth’s economic system might stop growing from the reduced availability of resources, increased pollution levels, and continued population growth. The policy prescription would be to not only control population growth, but also to curb material consumption. There have been many debates about these estimates and prescriptions. Mainstream economists have been very vocal critics of this approach, reiterating that markets and price incentives would ensure reallocation of resources, technological innovations, and improved efficiency.

Not only does the measure of the carrying capacity differ, but also how different species approach the limits of the carrying capacity vary. Two different potential paths for species have been identified by ecologists, referred to as the K selection and the r selection. In the former, the growth rate of population at the initial stages when there is an abundance of life-supporting resources like food is very steep. As the availability of fixed resources becomes scarce, the population growth rate drops and the total population approaches the carrying capacity asymptotically¹ (See Figure 6.2). In the latter situation, the growth rate of population continues to rise at an increasing rate as long as there is some resource available, independent of the extent of scarcity of the resources. The growth rate may continue to rise at the same rate even after the available resources are exhausted. This, of course, cannot be sustained, and there is a sudden sharp drop in population, as deaths exceed births because of the unavailability of resources. If resources are renewed, then once population is small enough such that there is adequate availability of resources, then the growth rate may increase sharply again, resulting in a cyclical rise and fall of growth around the limits determined by the carrying capacity.

Figure 6.2 Different population dynamics

In our discussion so far, we have talked about the biophysical aspect of the carrying capacity of an ecosystem. Biologists point out that every species has its own rules of social behavior and minimal requirements of resource including space. This is easier to visualize in the context of human beings and their social systems. Different cultures have different conceptions of personal space, which depend not only on social norms and preferences, but also on incomes and availabilities. Hence, distinct from the biophysical carrying capacity, ecologists also talk about a social carrying capacity that tries to estimate the maximum population that can be sustained under different social systems. The social carrying capacity is usually substantially lower than the biophysical carrying capacity.

Measuring Sustainability from the Demand Side: Ecological Footprint

Initially proposed by Wackernagel and Rees (1995), the ecological footprint was adopted and popularized by Redefining Progress and the WWF (McLellan 2014). As the name suggests, the term ecological footprint refers to the imprint one leaves behind on the ecological environment as a result of one’s economic and social activities. More specifically, it is a measure of the biological capacity of the earth that is demanded by a person, a population, or specific human activities such as production and consumption. In many ways, this is a better measure than the carrying capacity because it uses actual data that is not subject to uncertainties and other inaccuracies. The measure reflects our preferences and choices, and in this sense, it can easily be correlated with the environmental stress that our behavior creates. Also, it indicates how much of the earth’s carrying capacity would remain for other species to thrive in, as humankind is just one of the many species sharing the same planet, and the greater demand humans make on the planet, the less ecosystem services are available for the rest.

One simple way of measuring the ecological footprint is to first find how much environmental space is available for a particular resource at a moment of time. The definition of environmental space is the global resource available at a moment of time divided by the global population at that same moment of time. It is a quick measure of the per capita availability of a resource (see Figure 6.3). To take an example, if there is a 100 acres of bioproductive land available at a moment of time and the total population is 50, then environmental space is 100/50, that is 2 acres per capita. Environmental space could be computed for a community, state, nation, or the world. This is useful because a country’s consumption of some resource can then be compared with that of other countries quite easily and benchmarked along an accepted international norm. Policy prescriptions could also be generated from these measures. If the resource use or pollution created is more than the global average or an accepted norm, then one can follow conscious policies to reduce use. The converse, however, is not a good idea as the intent should always be to reduce the ecological footprint so as to make available environmental space for other species. The concept is static in nature, in that it assumes a fixed set of technologies and unchanging human behavior.

Figure 6.3 Constituents of the ecological footprint

Another measure to estimate the ecological footprint is using the concept of net primary productivity (NPP). All food and fiber, as well as mineral ores, come from nature. Food and fiber comprise renewable resources, and all food comes from plants using solar energy through photosynthesis. A common measure used by ecologists is net primary production, defined as the amount of plant material produced on earth, that is, the net amount of solar energy converted to plant organic matter. Another way of looking at NPP is the amount of energy obtained after subtracting the respiration of primary producers from the total amount of energy that is fixed biologically through photosynthesis. It is indeed the total food resource available on the earth for all species. The rate at which humans consume NPP is an important measure of the human impact on the functioning of the biosphere. The more we consume, the less is left for others in the food web. Various studies (Krausmann et al. 2013) have estimated that humans now appropriate anything from 24 to 32 percent of NPP for their own use. While the total appropriation is still not considered alarming, the growth rate of appropriation is approaching alarming limits. However, there is considerable concern over rising inter-regional variations in NPP.

The food web in which NPP is considered as the primary fuel operates in ways that human beings are not accustomed to thinking about. There is a famous example given by an American chemist, Miller (1971). He claimed that “300 trout are needed to support one man over one year. The trout in turn has to consume 90,000 frogs that must consume 27 million grasshoppers that live off 1000 tons of grass.” This illustration indicates that the consumption of 300 trout actually requires far greater space than we normally suppose. It is evident also that, as a typical human being consumes many more things than mere trout, and the fact that human population has been growing quite rapidly in the recent past, the magnified impact of our food habits on the environment can be quite substantial, significantly higher than what we are accustomed to imagine.

Another measure that is commonly used is called IPAT (Ehrlich 1968). It provides a quick measure of the impact of human economic activities on the environment. This measure is particularly useful as a tool when we think of incremental changes. The formula I = PAT measures I, the environmental impact, which is the product of P, population, A, affluence and consumption, and T, the technology of resource use and waste. Population data is easy to obtain, but separate quantifiable data on technology or affluence is not easy to get. Hence, often A and T are clubbed together and measured in terms of per capita energy use. As an illustration, consider I = PAT in incremental terms. Suppose P doubles in the next 50 years and affluence (through economic growth) increases fivefold at current technologies. Then, I = PAT would be I = 2 × 5 × 1 = 10, that is, there would occur a tenfold rise in environmental impact. If we need to keep the environmental impact even at the current level, there has to be a tenfold reduction in resource use and waste creation! This would be quite a challenge for human ingenuity to come up with technological breakthroughs that would reduce resource use in the light of increasing population and increasing per capita energy demands. At the same time, this could be achieved through a change in consumption patterns, but lifestyle changes could pose an even greater challenge.

The simplicity in understanding the implications of the ecological footprint has resulted in the development of several tools to measure individual footprints based on lifestyle choices (http://ecologicalfootprint.com/, http://footprint.wwf.org.uk/). The concept has further branched out into carbon and water footprints as well (McLellan 2014). However, there are several limitations of the measure of ecological footprint. To start with, as it is measured at a point of time, it does not embody the dynamism of technological progress or changes in consumption patterns. A time series of data on the ecological footprint can help circumvent this limitation. A comparison of ecological footprints across nations can provide an accurate overview of the spatial disparities in affluence and consumption patterns, which could help in better formulation of policies at a global level to reduce the overall ecological footprint for the global population.

Ecologists usually have in place some approximations of the regeneration rates of natural resources, and hence ecosystem services. The carrying capacity is an example of such a measure. A quick comparison of the ecological footprint with these measures provides an estimate of the extent to which humanity is using nature’s resources faster than they can regenerate. This interaction between the demand and supply of ecosystem services is captured in a concept called ecological overshoot, which is discussed next. The enormity of the problem of ecological overshoot is evident from Boxes 6.4 and 6.5, which discuss the heinous impact of anthropogenic activity on the ocean ecosystem.

Box 6.4 The Great Pacific Garbage Patch

Box 6.5 Dead zone in the Gulf of Mexico

Ecological Overshoot

When humanity’s ecological resource demand exceeds what nature can supply, an ecological overshoot is reached. It implies that we are essentially overdrawing resources at a rate faster than they can be replenished. This affects not only the quantum of resources, but also the flow of ecosystem services, as it interrupts biogeochemical cycles. Box 6.6 illustrates the extent of potential danger to the earth from overshoot using the concept of the Earth Overshoot Day. Looking at it more directly, overshoot would result in collapsing fisheries, species extinction, deforestation, loss of ground water, and carbon-induced climate change. Thus, overshoot is about the mismatch between the ecological footprint and carrying capacity, both of which can rise or fall. Here, the carrying capacity is looked at not in terms of the extent of human activity that can be supported, but in terms of biophysical capacity of resources. These resources include bioproductive land, bioproductive sea, energy land, built land, and biodiversity. From these resources, we obtain food and fiber, as well as energy, and this is where we also release our wastes. Specifically, bioproductive land refers to the land requirement for production of crops and timber and for use as pasture. Bioproductive sea is the sea area providing fish and seafood for human and animal consumption. The land required to grow new forests to act as absorbers of CO₂ to offset the CO₂ generated from burning of fossil fuels for energy is referred to as energy land. Built land is land that is no longer bioproductive, as it houses buildings factories and other physical infrastructure. Biodiversity refers to the area of the land to be set aside to preserve biodiversity. The unit used to measure biocapacity is a productivity weighted average of biological capacity of different pieces of land in the world (or nation), called the global hectare (gha).

Box 6.6 Earth Overshoot Day

Data from the Living Planet Report 2014 demonstrates that the average ecological footprint per person worldwide was 2.6 gha. In 2010, the amount of productive land and sea area available (biocapacity) in the world per person was 1.7 gha. The amount by which humanity’s footprint exceeds the planet’s regenerative capacity is about 50 percent. If the world continues its business as usual mode, then, by the middle of the century, we would require two-and-a-half planets or more, depending on how high the standard of living becomes between now and then. On the other hand, it is obvious to live sustainably on one planet, humanity’s footprint needs to come down dramatically within the next one or two decades. A stylized depiction of this is represented in Figure 6.4. This means that 1.4 earths would be required to regenerate humanity’s current demand. We do know that national ecological footprints can vary largely. The United States has the largest footprint, and if the rest of the world lived like the average American, we would need around 5.5 planet earths! (see Figure 6.5) The same report suggests that, compared to 1961, the global ecological footprint has increased by 2.5 times while the biocapacity available per person during the same period diminished by 50 percent. In 2010, out of humanity’s total ecological footprint accounted for by CO₂ emissions (carbon footprint), the number of countries with a biocapacity deficit (that is where per capita ecological footprint exceeded per capita biocapacity) was 91 out of 152 countries. It was also noted that 85 percent of the global population lived in countries with a biocapacity deficit (McLellan 2014). This picture clearly reveals the rather alarming extent of ecological overshoot, and unless something is done urgently and decisively to change the situation, ecological disasters remain a distinct possibility.

Figure 6.4 The number of earths needed to sustain humankind

Figure 6.5 If everyone in the world lived as they do in the United States it could require five and a half planets to live sustainably

Sustainability Indicators

Measures and indicators of sustainability are complicated for the simple reason that they must be able to indicate what damage is being done to the environment at present along with what it implies for future generations’ opportunities. These opportunities, to be sustainable, must be similar to the ones the current generation is presented with. Broadly speaking, there are three sets of indicators, one set that is specific in nature such as pollution or the extent of degradation at local levels that can be aggregated over time or across space, but do not necessarily allow a composite understanding of the implications. The second set of indicators is composite in nature, which tries to compensate for the heterogeneity of the micro and specific indicators. The third set of indicators are macro or global in nature, which tries to accommodate, in a single measure, the state of sustainability of a nation or region of world. The extent of information conveyed by composite indices makes them useful, despite their other drawbacks.

As an example of a specific indicator, we could consider the measure of quality of water in inland water bodies. We would still need to know the benchmarks such as the tolerance limits for regeneration. There are a large number of such measures developed by many organizations, which cover a large variety of sustainability issues. For example, the European dashboard of sustainability indicators (Stiglitz, Sen, and Fitoussi 2009, p. 235) covers 10 different sustainability themes with 11 level-one indicators, 33 level-two indicators, and 78 indicators for level three. Level-two and level-three indicators cover 29 subthemes. Some of these indicators, like GDP are very global, whereas a measure of the percentage of smokers in a population is very specific, and they do not lend themselves to an immediate interpretation of their implication for sustainability. Such dashboard measures are difficult to use because of the extent of their heterogeneity. Nevertheless, they are useful in terms of their information content, and a follow-up strategy might require the development of more quantitative information so that it can inform policy formation and target setting. In a fundamental sense, sustainability is multidimensional, which implies more than one indicator is required to represent it.

However, parsimony is equally desirable. One way to circumvent the extreme heterogeneity of dashboards is to create composite indices (ibid, p. 237). Sometimes existing indices, such as the HDI, are scaled-up to include environmental issues, combining it with information on pollution, for example. Another well-known index, the Osberg and Sharpe (2002) Index of Economic Well Being (IEWB) measures consumption, sustainable accumulation, and social issues related to reducing inequalities and vulnerabilities. Such composite indices can also be inadequate as far as sustainability is concerned. For example, the IEWB focuses on social disparities for a particular generation. It falls short of measuring sustainability, both in the context of future generations and with respect to the availability of natural resources and ecosystem services. Over a period of time, it may be found that, in a country, there is an increasing divergence between GDP and IEWB measures. On the face of it, it might appear that there is a problem about sustainability of the economy. Yet, it could be entirely accounted for by a failure to reduce current economic inequalities. Any conclusion about the state of the natural environment would not follow from this measure.

Some other popular composite indices are the ESI, environmental sustainability index, and the EPI, environmental performance index (Esty et al. 2005). ESI covers five domains, namely, environmental systems, environmental stresses, human vulnerability, social and institutional capacity, and global stewardship (managing common environmental problems). This is a composite of 76 variables. EPI is a reduced form of ESI based on 16 outcome indicators, making it useful for policymakers to see whether targets are achieved. Here again, one problem remains in terms of the inability to indicate a norm or threshold value beyond which one could conclude that a particular country is on a unsustainable path.

Many years ago, Samuelson (1961) and Weitzman (1976) had argued that a correctly adjusted NNP, where all relevant depreciations of capital were accounted for, should equal the maximum level of sustainable consumption that can be reached for the present and for the future. The recently proposed, more fashionable, green NNP, which takes into account the consumption of natural capital, does provide a picture of how much of resources are used up in production, but does not actually tell us whether the level of consumption is unsustainable or not in itself. There is another important set of problems with green NNP with respect to the valuation of natural assets and their consumption. Market prices are either absent or are inaccurate estimates of true costs. Quite often, the methods of valuation that do not depend on market prices can be somewhat arbitrary where the valuation is extracted from a what if hypothetical kind of situation and considered to be speculative in nature by many accountants (Dasgupta 2001, 2009; Kolstad 2000).

Green NNP, despite all its measurement-related problems, is useful only to the extent that it indicates the amount of depletion of natural capital for the particular year. It does not tell us whether the society is over-consuming or under-investing in an unsustainable manner. This is a more dynamic question, the answer to which cannot be obtained by looking at a particular year’s measure of green NNP. What it might help us in terms of policy measures is the knowledge of the kinds of natural capital being depleted and whether they are considered to be non-substitutable like biodiversity or other biogeochemical ecosystem services.

Another quite frequently used measure of sustainability for an entire economy is adjusted net savings (ANS), which relates to the changes in net wealth of the economy. This, in some sense, builds on the concept of green NNP, but in some sense, goes further in taking into account the stock of wealth (rather than the flow of national income). This particular measure was developed by the World Bank (Bolt, Matete, and Clemens 2002; Pearce, Hamilton, and Atkinson 1996) for almost all countries of the world. The measure is derived from standard national income accounts. Four types of adjustments are made to the estimates of gross national savings. First, the capital consumption of produced assets (depreciation) is deducted. Second, current expenditure on education (conventionally treated as consumption) is added to the savings figure. The third adjustment deducts the value of the depletion and extraction of natural capital. Finally, the country’s CO₂ emissions, responsible for global pollution damage, are deducted. This country-wise measure is regularly computed and is readily available in the World Bank database. One observed limitation of this measure (when making comparison across countries) is that the first two adjustments account for the largest deviations across countries. Hence, differences in this measure across countries may not necessarily help us conclude that the one with the higher ANS is contributing to an improved ecological environment.

The discussion so far indicates the difficulty in obtaining a satisfactory aggregate measure of sustainability. In its absence, we may have to deal with imperfect measures, and there could be a large number of these, down to the local micro-level measures of environmental degradation. One reason why these measures remain unsatisfactory is the fact that measuring sustainability requires not only current statistically obtained observations, they need relatively accurate projections about the future. These projections will have to include technological and environmental trends, as well as trends in social institutions and political forces. There is also a need to look at the interaction between these two types of trends. Hence, such projections, especially the ones of social and political trends, entail specific answers to normative questions. Finally, sustainability is a global problem. It is not about assessing the position of each country as isolated entities. It is more about trying to look at the contribution each nation might be making to global sustainability.

Toward a Framework for Sustainability Indicators

To be effective in terms of information content, as well as providing adequate signals for policymaking, sustainability assessment would require both global measures along with well-identified dashboards of specific indicators. It is further desirable that the components of the dashboards should be interpretable as variations in the stocks of some assets. It is important to not only have a reasonably accurate valuation of these stocks, but also to have an understanding of critical thresholds of certain vital stocks, which would be in terms of physical measures. Indeed, there should be a subset of physical indicators, carefully chosen, on the environmental aspects of sustainability.

A conceptual framework for measuring and tracking sustainability was developed by the Joint UNECE/Eurostat/OECD Task Force on Measuring Sustainable Development (2013). The purpose of the framework was to pool together the different sets of indicators produced by national and international organizations. From this set, the task was to create a list of potential indicators, which would be based on one single conceptual framework and help in comparing and harmonizing different sets of indicators that are estimated around the world. The framework distinguished between three conceptual dimensions of human wellbeing. The first related to the present wellbeing of the generation in a particular country (referred to as the here and now). The second would be the well-being of future generations (referred to as later). Finally, there would be the wellbeing of people living in other countries (referred to as elsewhere). Thus, both the spatial and temporal aspects of sustainability are covered by the framework. Twenty subthemes, covering social environmental and economic aspects, have been identified, including subjective wellbeing, health and education, income, physical safety, trust, as well as energy sources, land, and ecosystems along with knowledge and financial capital.

Table 6.1 illustrates the 20 subthemes that were selected in developing the framework, as well as where they were relevant in the three dimensions discussed. For instance, land and ecosystems would be important for both the here and now and elsewhere because they are global in nature, as well as relevant for later because sustainability concerns would require a minimum quality of this indicator. Themes like nutrition or leisure are only relevant for the here and now. They have no trans-boundary impact. The later availability of these would be determined by the accumulation of capital, which is considered as separate themes. The framework also goes into identifying how to measure the conceptual categories indicated. For instance, health in the here and now could be measured by life expectancy at birth. The same measure would also be valid for later. The corresponding policy indicators would include health expenditure, specific issues such as instances of prevalence of smoking, or suicide rates, or mortality, in addition to life expectancy. A smaller set of more specific indicators is provided in the framework for the same 20 themes. For instance, labor and education could be indicated by employment rate and educational attainment, respectively. Air quality could be determined by exposure to particulate matter, physical safety through death by assault or homicide rates. These, as is evident, would provide a small minimal set of indicators, which would give not only a quick immediate indication of some aspect of sustainability, but also allow a similar set of indicators from every country to be comparable.

Table 6.1 Framework for measuring sustainable development: Relationship between the conceptual and thematic categorizations

Source: Adapted from UNECE/Eurostat/OECD (2013).

In this chapter, we have provided a quick overview of the large variety of measures and indicators of sustainability. The measures may be inadequate or imperfect in many ways, but that is only to be expected. The inadequacy arises out of the difficulty in making projections of future trends, as there is a value judgment that needs to be exercised. The imperfections arise from the difficulty of measurability of the value of natural goods and services and the costs of environmental damage. Markets for these types of goods and services do not exist, which means that prices cannot be observed. We now turn our attention to why markets sometimes fail to account for all the social costs and benefits of human activities.

¹ The term asymptotically means approaching a value or curve arbitrarily closely (i.e., a limit is approached).