Introduction

This chapter will try to draw a bigger picture about the likely future changes in age distribution in the countries of Southeast Asia, and highlight some key dimensions of the expected population ageing. It will focus on the demographic core of population ageing and also cover the changing education and health distributions of the population which are key dimensions for assessing the likely implications of these trends for individual countries. We will do so not in the conventional way of presenting already existing population projections for different countries (for example, taken from the U.N. population projections or national projections), but rather we will present innovative methods of population projections, such as probabilistic projections and multistate projections, and combine them with unique new data from a global ageing survey conducted by the Oxford Institute of Ageing funded by HSBC. These new data, combined with those more sophisticated projection methods, will allow us to address some of the key challenges of population ageing much more directly. We will present these analyses here for a few selected countries.

The chapter will be structured in the following way: First we present some new probabilistic population projections for Southeast Asia and specifically for Singapore. While these provide a comprehensive picture of what is likely and what is uncertain in terms of future population size and structures by age and sex, the ensuing sections of the paper also consider the changing educational structure of the population, which has major impacts ranging from effects on demographic trends themselves, to effects on health and income, among others. In the remainder of the chapter, we take a closer look at expected future trends in health and disability and how the explicit consideration of educational health differentials, together with a changing educational composition of the population, influences the outlook for ageing-related health concerns.

Probabilistic Population Projections for Southeast Asia and Singapore

There has been a major upsurge in probabilistic population projections recently because this field offers several advantages compared with conventional population projection variants or scenarios. As compared to the traditional U.N. high-medium-low variants, which are based only on alternative fertility assumptions and otherwise consider identical mortality and migration assumptions, probabilistic population projections consider the full range of uncertainties in all three demographic components of change.

Factors driving previous population growth

The broad outlines of the history of global population growth are by now familiar. At the dawn of the agricultural revolution (8000 years before present), total population was about 250 000 (Cook 1962). It took all of human history (until 1800) for global population to reach one billion – roughly today's population of Europe and North America combined. It took 130 years (until 1930) to reach two billion. It took only 60 more years (1960) to reach three billion. The fourth billion was reached between 1960 and 1975, the five billion mark was passed in 1987 and the six billion mark was reached in 1999.

Less well appreciated are the facts that both the annual growth rate and the annual absolute increment of world population have passed their peaks and are expected to continue to decline. The growth rate peaked at 2.1% per year in the late 1960s and fell to 1.35% by 2000 (see table 6.1), and the annual absolute increment to population peaked at about 87 million per year in the late 1980s and was about 81 million at the end of the 20th century. This does not mean, of course, that little further population growth is to be expected; most mid-range population projections foresee future population rising to 8–10 billion by the end of the 21st century.

As shown in table 6.1, the TFR (average number of children per woman under a period perspective) declined modestly in most parts of the world from 1950–1955 to 1970–1975, then declined over the following 25 years with a rapidity that was unimaginable in the 1960s.

Dramatic changes in demographic patterns have taken place over the past several decades, particularly in less developed countries (LDCs). Mortality and, subsequently, fertility have fallen at rates much faster than rates of decline experienced in the industrialized countries. Unlike the more developed countries (MDCs), demographic transition from high to low fertility is not yet complete in many LDCs. In this chapter we summarize the current demographic situation and discuss factors behind the demographic transition in LDCs. This discussion provides background for the exploration of population–development–environment interactions taken up in Chapter 3 and in Part II of the book.

In addition, we discuss projected trends in population growth and aging over the 21st century based on the most recent projections of the International Institute for Applied Systems Analysis (IIASA). There appear to be three virtual certainties: world population will rise significantly from its present level of around 6 billion, although it may start to decline during the second half of the next century; its distribution will continue to tilt from MDCs to LDCs; and it will continue to age. Probabilistic projections indicate that global population is unlikely to double from its present size; on the other hand, a severalfold increase in the size of the population above age 60 is virtually assured. The 60+ age group, measured as a proportion of total population, will almost certainly double and will likely triple during the course of this century. The most important source of uncertainty in population projections is the future path of fertility, although the impacts of alternative trends in mortality and migration are significant as well.

While recent international agreements have recognized relationships between population and global environmental issues, none has translated these linkages into specific recommendations. On the environment side, Agenda 21, signed at the Earth Summit in 1992 and intended as a blueprint for sustainable development, recommends only that nations take demographic factors into account in the policymaking process. On the population side, the Programme of Action agreed to at the International Conference on Population and Development in Cairo in 1994 also discusses population–environment links, but does little more than repeat the language of Agenda 21.

One logical forum for analysis of relationships between population and climate change is the Intergovernmental Panel on Climate Change (IPCC), which is charged with assessing the science of climate change and its potential impacts, as well as formulating response strategies. Yet it has paid little attention to population. For example, the IPCC's most recent reports on mitigation and adaptation options (Watson et al., 1996; Bruce et al., 1996) evaluate a wide array of strategies but do not consider policies to slow population growth. There are likely a number of reasons for this omission, not least the tension between North and South over the relative contribution of population and consumption to environmental problems (Bongaarts et al., 1997).

In Chapters 4 and 5 we examined the role of population growth in generating greenhouse gas (GHG) emissions and its impact on the ability of societies to adapt to climate change. Chapter 4 concluded that under conditions of rapid demographic transition (lower fertility and lower mortality, resulting in slower population growth and an older population age structure) GHG emissions would be reduced relative to emissions in a baseline demographic scenario.

As pointed out in Chapter 1, historical greenhouse gas (GHG) emissions have committed the world to some climate change even if aggressive mitigation policies are put into place immediately. Societies therefore have an incentive to plan for adaptation to climate change impacts no matter how much emissions are reduced. In this chapter, we ask whether slower population growth would enhance the ability of institutions, especially in developing countries, to adapt to the likely impacts of climate change. In 20, 50, and certainly in 100 years, some countries that are currently poor will no longer be so. However, others will, and large subpopulations may remain poor even in countries that attain average living standards much higher than they enjoy today. In considering the impacts of climate change, it is important to impose a hypothetical unfavorable climate not on the world of today, but on the world as it may be decades in the future. Nonetheless, both the geographical distribution of expected climate change impacts and a concern for equity suggest a focus on low-income settings.

We focus on three aspects of human welfare that may be threatened by climate change: agriculture, health, and environmental security. In Chapter 3, we developed a model of population–economy–environment interactions, emphasizing the theme that while stresses to populations in low-income settings can set off a destructive series of effects, policy intervention can encourage virtuous responses as well. Vicious-circle reasoning is also key to our understanding of how population growth affects the ability of societies to respond to the threats posed by climate change in these three areas.

The first task in formulating a reasonable partitioned model is to determine how much energy in more developed countries (MDCs) and less developed countries (LDCs) is consumed at the level of the household. A portion of this amount is then attributed to “household overhead,” that is, that portion of household energy consumption which is independent of the number of members.

MDCs. In MDCs, the residential/commercial sector, the transportation sector, and the industrial sector each account for about one-third of all final energy demand. Direct energy use in homes (i.e., heating, electric appliances, hot water) accounts for 20% of final energy demand or about one-quarter of primary energy (the greater share of primary energy results from the important role of electricity in the household energy supply). If energy for personal transportation (about 15% of primary energy) and energy expended in residential construction and the production of household goods (together about 10% of primary energy) are also assigned to households, it can be estimated that about one-half of all MDC energy use consists of consumption at the level of the household.[1]

Data on US households indicate the presence of strong economies of scale in the residential and transportation sectors. Table A.3 gives the average household expenditure for direct residential and household vehicle energy consumption (EIA, 1990). These two sectors comprise 20% and 13% of total US final energy demand, respectively. Household energy use is related to household size using both linear and log-linear (constant elasticity) relationships.[2] Both specifications indicate that household overhead (the y-intercept) is 40–50% of average household vehicle energy use and 60–65% of direct residential energy use.

Demographic trends and climate change will be two important themes of the 21st century. Both areas have been researched intensively, yet relatively little attention has been paid to the relationship between them. This book aims to describe that relationship.

The book is divided into two parts. In Part I, we discuss the climate outlook, demographic prospects, and economic perspectives on population, development, and the environment. These chapters take as starting points existing reviews of each field: the latest assessment of the Intergovernmental Panel on Climate Change (IPCC; Bruce et al., 1996; Houghton et al., 1996.; Watson et al., 1996); the documentation for the global population projections of the International Institute for Applied Systems Analysis (IIASA; Lutz, 1996); and a chapter on economics, demography, and the environment from an assessment of the social scientific aspects of climate change (Rayner and Malone, 1998). In Part II we analyze three major links between population and climate change: the role of population growth and structure in greenhouse gas (GHG) emissions, the effect of population growth and structure on the resilience of societies to the expected impacts of global warming, and the implications of global warming for population-related policies.

Chapter 1 reviews the natural science aspects of climate change and describes how the Earth's natural greenhouse effect is being enhanced by emissions of carbon dioxide and other GHGs originating from human activities – principally the burning of fossil fuels such as coal, oil, and natural gas. In the absence of restrictive policies, continued population growth and increases in economic output are expected to drive emission rates higher in the future. How much and how fast climate will change as a result are uncertain.

The threat of human-induced climate change, popularly known as global warming, presents a difficult challenge to society over the coming decades. The production of so-called “greenhouse gases” (GHGs) as a result of human activity, mainly due to the burning of fossil fuels such as coal, oil, and natural gas, is expected to lead to a generalized warming of the Earth's surface, rising sea levels, and changes in precipitation patterns. The potential impacts of these changes are many and varied – more frequent and intense heat waves, changes in the frequency of droughts and floods, increased coastal flooding, and more damaging storm surges – all with attendant consequences for human health, agriculture, economic activity, biodiversity, and ecosystem functioning.

Because the impacts of climate change are expected to be global and potentially severe, and because energy production from fossil fuels is a fundamental component of the world economy, the stakes in the issue are high. At the same time, a number of aspects of climate change complicate the problem. First, while much is known about the factors governing climate, considerable uncertainty remains in projections of how much climate will change, how severe the impacts will be, and how costly it would be to reduce GHG emissions. Second, because the impacts of today's GHG emissions will be felt for decades into the future, it is not possible to wait and see how severe impacts will turn out to be before taking preventive action. Therefore, if emissions are reduced now, the costs will be borne in the near term while the benefits, which will depend on uncertain projections of future impacts, will be realized largely in the long term.