 |
|| Home || Search || Contact || Publications Eshop || Privacy Statement ||
Global Population Projections - Is the UN getting it wrong? by Ron Duncan and Chris Wilson
February 2004
RIRDC Publication No 04/041 RIRDC Project No ANU-51A
Many extravagant extrapolations of this period of rapid population growth were made with little appreciation of why it was occurring. There are now other dramatic changes in population growth and structure underway and there appears to be even less awareness and understanding of what is happening and what is likely to happen to population growth and structure over the next 20 to 30 years. The world’s population has entered a phase of rapidly slowing growth and eventual population decline in many countries because of the extension of the below replacement fertility rates being experienced in developed countries to developing countries.
The changes of the past 50 years have at times been poorly forecast by demographers, including the United Nations’ Population Division, which has responsibility for global projections. While they have understood some of the changes taking place, they have not performed well in guessing the magnitude of the changes. The changes in the most important factor of all—the fertility rate—are hardly understood and have been very poorly forecast. If demographers had anticipated the changes much better, maybe we could have been spared some of the more outrageous claims by proponents of population control and, more recently, by those concerned about environmental issues.
Understanding demographic change is very important for long-term policy making. There has recently been a wider grasp of the fact that the populations of many countries are aging rapidly. This has implications for all kinds of public policy: health and education facilities, pension plans, housing, food production, research and development, and so on. However, the rapidity of the reversal in population growth in some countries and the decline in population that is in prospect has received almost no public attention.
This paper traces the major changes in the global population over the past half-century and examines the reasons for the very rapid growth, particularly in the poorer countries. It discusses why the projections of population growth by the body with responsibility for such projections have at times been misleading. The paper also discusses current projections, looking at recent trends in fertility rates and life expectancies and what these are likely to mean for global population growth and growth in particular regions and major countries. Of particular concern is that the UN appears to be underestimating the future decline in fertility rates, despite all evidence to the contrary. As a result the latest long-run global population projections appear to be much too high.
The demographic transition—the shift from high to low mortality and fertility rates—in lowerincome countries, as previously experienced in the now high-income countries, resulted largely from the provision of clean water and sanitation, pesticides, and vaccinations against major infectious diseases, as well as improved living standards. The improved health conditions led to shar
reductions in infant mortality. In turn, this meant that women did not have to bear as many children as previously to be assured that there would be sufficient offspring to look after their parents in their old age.
At the same time as infant mortality and fertility rates were declining, the health and life expectancy of the remainder of the population was improving as incomes were rising and food production was increasing. In spite of the Malthusian concerns, world food production outpaced population growth in this period of the most rapid population growth in the world’s history.
The fastest population growth took place in those countries where the fertility rate did not fall as quickly as the mortality rate. The resulting rapid increase in cohorts of young people led to a longerterm increase in population (“population momentum”) even though fertility rates continued to decline.
The demographic transition is now over for most developing countries. Most of these countries now have total fertility rates (TFRs) below 2.1 per cent, the replacement rate. However, their populations will continue to increase for some considerable time because of population momentum. But with life expectancies continuing to increase and fertility rates still declining, populations will age rapidly.
Presently, the most dramatic cases of aging of the population are taking place in Italy, Japan and Spain. Japan’s TFR has been below the replacement rate since the early 1970s and has continued to fall, reaching 1.3 per cent in 2000. The TFR in Italy and Spain has been below 1.2 per cent since the mid-1990s. The UN Population Division estimates that in 2002, 24 per cent of Japan’s population were 60 years or older. It is estimated that by 2050 around 42 per cent of the population will be 60 years or older. Below-replacement fertility rates will eventually lead to population decline. Japan’s population, for example, is expected to begin to decline from 2007.
Key questions for demographers and policy makers are whether the below-replacement fertility rates being experienced in all northern, southern and western European countries, and elsewhere, will continue their downward path, and whether developing countries face similar trends? As evidenced by the experience in Hong Kong, Singapore and South Korea, the decline in fertility rates in the present developing countries could be even faster than in the developed countries. For example, the TFR in Hong Kong in 2000 was 1.17 per cent—below that in Italy and Spain—while the TFR decline in South Korea has been faster than in Japan.
In its year 2000 “medium variant” projection to 2050, however, the UN Population Division has assumed that the TFR will stabilise around 2.1 per cent in most developing countries and move back towards the replacement rate in those higher income countries where the TFR is already well below the replacement rate. These assumptions mean a considerable increase in the TFRs in countries such as Hong Kong, Singapore and South Korea, for example. They also mean an increase in the TFR in China. The UN Population Division may be making serious mis-judgements in the most important assumption underlying its population projections.
A review of past UN population projections shows that there have been systematic biases in their assumptions about future trends in important factors. The most significant errors have been the consistent over-estimation of fertility rates in both developed and developing countries. The speed of the decline in fertility in the last one-third of the 20th Century consistently surprised the UN. The increase in life expectancy throughout the world has been almost as consistently under-estimated.
However, the impact of under-estimating the increase in life expectancy has been not as important for population projections as the bias in the fertility assumption. Of the variables underlying population projections, the behaviour of the fertility rate is the least well understood. Therefore, until understanding improves, the greatest uncertainty will attach to the fertility rate assumption. This means that most of the uncertainty in the population projections is the uncertainty about how many young people there will be.
Looking back at UN population projections, there have been three periods since 1957 when UN medium variant projections have significantly under or over estimated population growth. The first was in the late 1950s when forecasters were underestimating growth up to 1990 but overestimating growth to 2000, partly as the result of underestimating both life expectancy and fertility rates. In the late 1960s, population forecasts for the years 1990 and 2000 were again over-forecast, largely as the result of underestimating the decline in fertility rates. UN assumptions about fertility rates did not catch up with the trends underway until the mid-1970s. It is likely that the over-forecasting of population growth of the late 1960s gave some support to the “population explosion” and “resource depletion” scare scenarios being propagated at the time.
In the late 1980s and early 1990s the projections for the year 2000 population again became too high because the fertility assumption was over-estimating the trend. And again in the 2000 projection there has been a marked shift in the projections, basically as the result of a change in the fertility assumption. Whereas in the 1998 UN population projections the medium variant global population
projection for 2050 was 8.91 billion, in the year 2000 revision the projection for 2050 is 9.32 billion—an increase of almost 400 million.
The reason for this change in the 2000 projections is the revision of the fertility rates in developing countries—slowing the decline in the least developed countries, and in the “low fertility” developing countries increasing the fertility rates towards the replacement rate of 2.1 per cent. These revisions appear to be highly questionable. There is no sign of a turnaround in fertility rates in countries that have already reached very low levels. There is limited understanding of the reasons for the decline in fertility rates and for their persistence far below the replacement rate. Therefore, it appears heroic to assume an increase in the fertility rates rather than assuming rates will remain constant or continue to decline.
Given their population size, the future of fertility rates in China and India will have a large bearing on the global population. In the case of China, the UN has assumed an increase in the TFR from the present 1.8 per cent to 1.9 per cent in 2010-15 and thereafter. For Bangladesh and India the UN assumes that the TFR will continue to decline until 2025 and then hold at the replacement rate of 2.1 per cent.
The UN’s 2000 medium variant projections show the global population increasing to 8.27 billion by 2030 and to 9.32 billion by 2050. Whereas their global population projection for year 2030 published over the period 1994 to 1998 was reduced by over 500 million, in the projections published in 2000 they increased this projection by 160 million and increased the projection for 2050 by almost 400 million. The fertility rate assumptions that are the basis for this reversal appear to be highly questionable.
As stated earlier, the estimations of the degree of uncertainty associated with the UN population projections largely reflect the degree of uncertainty associated with the fertility assumption.
Estimations of the probabilities with the UN projections indicate that there is a high likelihood that the 2000 projection for 2030 could be 500 million too high or too low and that there is a low likelihood that the projection error could be as much as one billion too high or too low. Given the UN’s past performance in population projections, it is likely that their projections will be too high rather than too low.
The rate of growth of the global population is slowing rapidly and the projections of the population level to be reached in this Century have been falling for some time. Indeed, declining populations are now being projected for several countries and more are likely to be added to this list. Moreover, country populations are aging—in some cases, very rapidly—with declining fertility and increasing life expectancy. These changes in the trends and structure of populations have important implications, not least for food production.
|
