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\ A Compass to Lead us to the Future \ (Part One) Dr. Toshio Kuroda I. World Population Projection. (1) United Nations Activities on Population Projection. One of the extremely important activities of the United Nations, in relation to population, is the preparation for the future world population. This requires tremendous efforts to collect the most up-to-date data on population change, such as the vital rates of fertility, mortality and migration, and at the same time to evaluate and analyze them, and to examine the effects of economic, social and political change on components of population change. A critical purpose of world 'future population projection' is that it tells us the implications of both rapidity of increase and of the size of world population on the sustainable development of humankind, and even, on survival possibilities. Further, it also suggests the necessity of worldwide recognition of people who are focused on policy-making to address this so-called "population explosion", of which humankind has never before experienced in all its long history. World population projections recently published since 1992 and revised every two years up to 1998 show us remarkable changes in the world population size in 2050. Surprisingly, the world population projected for 2050 has shown a considerable reduction from 10.019 billion in the 1992 projection to 9.83 billion in the 1994 projection, 9.367 billion in the 1996 projection, and finally 8.9 billion in the 1998 projection. These figures are of course based on the medium variant scenario. This remarkable reduction of world population projected for 2050 in such a short period of projection-1.1 billion decrease from 10 billion to 8.9 billion-introduced an active discussion. One is a favorable view to support the rather rapid declining trend of world population growth rate reflected in the smaller size of projected world population. Another one is a statistical issue, arguing there is an underestimation of fertility decline in some areas like Africa and Western Asia. The United Nations estimated "the day of 6 billion" to be October 12, 1999, which also contributed to raising people's concern about world population issues. On the other hand, the United States Bureau of Census published the different "the day of 6 billion", which is July 19, 1999. (2) Warning to Humankind. The most crucial significance of world population projection is its warning of the threat of population explosion to the survival of humankind. It is clear that human beings cannot increase infinitely as "Limit to Growth" demonstrates scientifically. The United Nations has made tremendous efforts to continuously publish world population prospects and to appeal to people to pay serious attention to the increase in global population. World population projections suggest that a world population of 10 billion in around 2050 will be inevitable, although recent projections show a declining trend. It seems to be reasonable to set a world population of 10 billion as a target to cope with emerging issues. It is proposed in terms of the carrying capacity of the earth. Very recently, an interesting symposium "The Age of 6 Billion: Can the Earth Feed Humankind?" organized by the Population Problems Research Council and the Mainichi Newspapers was held in Tokyo on September 4, 1999. It should be mentioned that Prof. Joel E. Cohen, who recently published an extremely useful book "How Many People Can the Earth Support?" (1995), was invited as a keynote speaker. He precisely and broadly examined studies made on this topic historically. He shows that in order to answer the question of "How many people can the earth support?" past attempts have ranged widely, from less than 1 billion to more than 1 trillion, and also that more than half of the estimates fall within a much narrower range, between 4 billion and 16 billion. It is very interesting to see from the distribution of the different sizes of projected world populations that the world population located at the center is 10 billion, which is approximately close to the size of the world population anticipated by contemporary writers. Of course, simple questions posed by the planet's human carrying capacity cannot be answered because it can be affected by the nature of economies, technology and levels of material well-being, physical, chemical and biological living environments, and is also related to the types of cultural values, and social, political and legal institutions. Consequently, population projections are usually shown by several scenarios composed of different sets of components. One of them located in the middle is assumed to be the most likely variant and is usually called the medium variant. (3) Is Projection Certain or Not? Population projection is not a prediction or a prophecy. It is often criticized that projected future population is not meaningful because it usually does not come true. This is based on a misunderstanding of the nature of population projection. Today, most population projections conducted by the United Nations, national organizations and other research organizations in the world are based on a component method. Major components of population change, namely fertility, mortality and migration are taken into account by assuming the course of future change in these three components. Of course, the changing course of these variables in the future is seriously examined based on the past trends, and are projected into the future based on an assumed course of these components. In other words, population projection is a conditional calculation of future population based on the assumed courses of change of component variables. IPopulation projection may be described metaphorically as a 'Ship's Pilot'. When a pilot recognizes a rock ahead, he is responsible to report that the ship will hit the rock if she does not change course. The role of population projection is like that of the pilot. Projected future population is not designed to tell certain figures in the future. However, demographers make every effort to project a future population which could be expected to be the "most probable". For that purpose, various projected figures based on different sets of changes of components-usually low, medium and high variants-are calculated. So that, the future population projection is essentially conditioned and assumed to be element-oriented, and does not predict a certain future population size. However, it is also desirable that projected future populations would be as close to the realized future population as possible. Here is a good example. The world population projection for 2000 made by the United Nations in 1960 was 6.1 billion, which is very close to 6.05 billion estimated by the United Nations 1998 Revision. The 1998 Revision for 2000 would be considered to be very close to the real world population. In this sense, the United Nations world population projection-medium variant-made in 1960 was fortunately appropriate in assuming future trends of fertility and mortality. On the other hand, to assume future trends of fertility and mortality for long-range projection-for example for one century, two centuries or more-is extremely difficult, particularly in the case of fertility trends. On the contrary, projection at short or medium-range is quite different in nature. For example, if we want to make a population projection for 2010 at the time of 1990, it will be much easier, because the population who will be aged 20 or over in 2010 are already living at the time of projection, 1990. So we can start with the exact numbers of people by age and sex gained from the population census. In this case, the population who are surviving at the age of 20 and over in 2010, are subject only to mortality rate by age and sex. The mortality changes which may be expected are usually rather stable. So the surviving population aged 20 or over in 2010 will be projected reasonably accurately. Unless mortality is affected seriously by the unexpected emergence of infectious disease or natural disaster, the population aged 20 and over projected seems to be reasonable. The only question is projection of the population aged less than 20 in the year of 2010. They are subject to a change in fertility and mortality during this 20-year period. Admitting that the mortality schedule is used to be significantly stable or showing a slow declining trend, fertility changes, however, are more difficult to assume. Even so, the projected population aged less than 20 may not greatly disturb the projected total population for 2010, because the majority of the population is aged more than 20 in 2010 and are affected only by the mortality schedule in terms of age and sex, which are considered to be quite stable. (4) Statistical Review and Appraisal. The population projection operation is basically composed of two kinds of work. One is a critical review of the trends of fertility and mortality in the past. The other is to assume their future trends from theoretical and practical standpoints, taking into account social and economic factors affecting vital events as much as possible. Recently, the International Institute for Applied Systems Analysis (IIASA) published the "Future Population of the World-what can we assume today?"- edited by Wolfgang Lutz in 1996, which is a critical study of assumptions of future world population projection. It may also be a critical response against the United Nations projections. The IIASA's comments were made from two points. One is concerned with the somewhat optimistic judgment of the United Nations on global fertility. They argue that fertility in Africa and Islamic countries may not be expected to decline to the level of replacement by 2050. In view of their massive population with high fertility, it could be difficult for the projected world population made by the United Nations to decline to the 8.9 billion-medium variant-in 2050. Secondly, the IIASA introduced nine scenarios based on possible combinations of scenarios by using high, central and low fertilities and mortalities. These nine scenarios were applied to different parts of the world. Central fertility, central mortality, and central migration assumptions are assumed to be the most likely ones. According to this approach, the world population would increase from 5.7 billion in 1995 to 7.9 billion in 2020 and 9.9 billion in 2050. The IIASA's projected world population in 2050 according to central fertility, mortality and migration is just one billion larger than that by the United Nations 1998 Revision. It should be noticed that the IIASA introduced many more patterns of future course of fertility and mortality in order to be able to respond to quite changeable combinations of fertility and mortality. However, the United Nations projections have only four patterns of variants, namely high, medium and low fertilities and constant fertility with only one mortality applicable to the four variants. Nevertheless, it is perhaps only the United Nations body that is capable of revising and publishing the world population projections every two years, due to the tremendous amount of manpower needed, including professional people and a global network for collecting up-to-date data. (5) Theoretical Question. Whether fertility and mortality will continue to decline infinitely or not is quite a difficult question. When we are making a future population projection extending over half-a-century or a century, how should the future course of fertility and mortality, particularly the former, be assumed? Whether the below-replacement level of fertility achieved in almost all the more developed countries, and numerous less developed countries, will continue to decline further, or recover the replacement level or go higher, is unknown. According to official United Nations estimates, which are updated regularly by the Population Division, 51 countries in the world, with 44 percent of the world population, had the below-replacement fertility in 1997. The Population Division projects that by 2015-in less than two decades-, 88 countries, with two thirds of the world population, will have the below-replacement fertility. The so-called demographic transition theory, drawn from Western experiences, theoretically explains the evolutional change of vital revolution by stages of three different combinations of high birth rate and high death rate, high birth rate and low death rate, and finally low birth rate and low death rate. The transition of vital rates in Europe is generalized into a demographic transition theory. However, this theory does not tell anything about future trends of fertility and mortality. In particular, if the below-replacement level of fertility (couples having fewer births than are necessary for generations to replace themselves) continues in those countries, their population will decline. In fact, population is already declining in a number of European countries. From the standpoint of population projection of the more developed countries as a whole, the United Nations assumed that their bellow-replacement level fertility would continue to rise up from TFR 1.59 in 1995-2000 to 2.06 in 2045-2050, returning to the replacement level. However, any theory demonstrating a future trend is not yet developed. In response to these new and urgent issues concerning fertility, the Population Division organized the Expert Group Meeting on Below-Replacement Fertility, which was held in 1997. Of course, there were not any decisive conclusions on the determinants of low fertility. It seems to be rational to say that the classical demographic transition is no longer applied in the new prevailing circumstances. The only important conclusion is that people have an underlying predisposition to reproduce, and consequently it appears unlikely that fertility will fall close to zero. Even one or two children might be enough to satisfy people's desire. Another important point proposed by the Population Division to the Expert Group Meeting was to keep fertility levels below the replacement level during the projection horizon of population estimates and projections by the United Nations. Accordingly, the world population projections by the United Nations 1998 Revision agreed to keep the below-replacement level of TFR up to 2050 in the more developed regions-1.82 in the period of 2045-2050-instead of 2.06 assumed by the 1996 Revision. It suggests that there is not any reasonable evidence or theory to assume a return to the replacement level or rising fertility. Finally, the United Nations is conducting another interesting world population projection, covering the period from 1950 to 2150, which is called a long-range population projection. A total of seven projections for each of the eight major areas of the world are considered in the long-range projections. The variants are distinguished by their assumptions regarding future scenarios for total fertility rates. According to the medium-fertility scenario, which assumes fertility will stabilize at the replacement levels of slightly above two children per woman, the world population will grow from 5.7 billion in 1995 to 9.4 billion in 2050, 10.4 billion in 2100 and 10.8 billion in 2150 and will stabilize at slightly fewer than 11 billion in around 2200. These long-range world population projections are providing ideas regarding the sustainable development of humankind and the supporting capacity of the planet. (6) Who Wants Population Projections? These days, population projections are increasingly important and critical work for demographers. What motivates them to prepare population projections, including sophisticated studies on statistical methodology? In the field of world population research, a future projection of world population has been a fundamental concern for the United Nations, international organizations and also social and natural scientists who are able to recognize the serious effects of a population explosion which has never happened in the history of humankind. Along with a dramatic increase in world population, a recent upsurge of environmental and global change research has come to heighten the demand for world population projection. Another field of study that routinely necessitates population projection is the analysis of world food consumption. Politicians, including public administrators, need population projections largely for planning purposes. Especially in the health, education and social security sectors, medium and long-term planners regard demographic variables as crucial components. The size and distribution of population by age and sex are also basic elements of population projections. For example, projections help decide where new hospitals and schools should be constructed, and how the legal system of pension payments should be organized to accommodate changes in the age composition of the population. The last group using population projections is the largest and the most heterogeneous. Many individuals, organizations and enterprises in the general public are interested in their specific standpoints regarding population projections. Aside from individual curiosity, their interest is used in the planning of future activities. These activities range from an individual's decision to pursue some activity, to an enterprises' marketing strategy for a commercial product such as baby food, or special products for the elderly. Lastly, in addition to those groups mentioned above, some specific groups explicitly use population projections for educational and illustrating purposes. For example, there are environmental and family planning groups who want to draw attention to what would happen in the distant future if policies aiming at a reduction of population growth were not implemented. In conclusion, although some uncertainty is more or less inevitable, population projection is greatly important as a compass to lead us to the future. The revising process, if taken continuously according to newly emerging changes in the assumed components, would be practically useful. The recent practice of the United Nations to revise projections every two years is a good example. Detailed discussion on how to calculate future population projection will be shown next in Part Two. |
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