Jumat, 24 Juni 2011

Population growth

After remaining at very low levels during most of human history, the average annual rate of population growth for the world began to accelerate at about 1700, when mortality in Europe started to decline steadily. Nevertheless, the rate of population growth did not rise above 0.5% per year until the first half of the 19th century and remained well below 1% per year until 1925 (Fig. 5.3). After piercing the 1% barrier in the late 1920s, World War II made the growth rate drop again below 1% per year during the 1940s, but the 1950s witnessed an unprecedented resurgence of growth fueled both by rising fertility in the more developed countries that experienced a “baby boom” after the war and by high fertility and declining mortality in developing countries. As mortality reductions in the developing world accelerated, so did population growth, with the result that during 1965–1970 the population of the world grew at more than 2% per year, a rate that, if sustained, would have led to a doubling of the world’s population in just 34 years. However, the late 1960s also marked the point where fertility in a number of developing countries began to show a clear tendency to decline As Fig. 5.4 shows, reductions in fertility became more clear cut during the 1970s and 
1500 1600 1700 1800 1900 2000 2100
Low Medium High
Figure 5.3
Average annual growth rate of the world population, 1500–2050.
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050
                                                                      Low Medium High
Figure 5.4
Total fertility at the world level, 1950–2050.

a declining trend set in. It is estimated that between 1960–1965 and 1995–2000, total fertility at the world level, that is, the average number of children women would have if they were subject during their whole reproductive lives to the fertility of each period, declined from 5 children per woman to 3 children per woman. Largely as a result of that reduction, the population growth rate declined from just above 2% per year in 1965–1970 to 1.35% per year in 1995–2000. Although this reduction has been sizable, the growth rate for 1995–2000 is still well above the levels prevailing during the first half of the 20th century and, if sustained, would produce a doubling of the world population in 51 years.
Today, the potential for continued population growth at the world level remains high, not only because further reductions of mortality are expected but also because many developing countries still experience moderate to high fertility levels and have, in addition, young populations where the numbers of future parents already surpass those belonging to previous generations. The term “population momentum” is used to denote the tendency of young populations to continue growing even when fertility declines significantly. To understand the mechanics of population momentum imagine a population with three generations: grandparents, parents and children. As the population moves from one period to the next, children become parents, parents become grandparents and the original grandparents die. For the population to stop growing, the number of children that parents have in a period must equal the number of grand-parents who die. If the population starts by having more children than parents and more parents than grandparents, when the children become parents their offspring will surpass the number of grandparents who die even if the new parents have only the children necessary to replace themselves. That difference will result in population growth.
What then are the prospects for future population growth? Population projections prepared by the United Nations (2001a,b) indicate that the world population will continue to rise over the next few decades but, because the rate at which population grows is expected to continue declining, there is considerable uncertainty regarding the size that the world population may attain in the future. In the United Nations projections future population growth is the result of assumptions made about the paths that fertility and mortality will take in the future at the country level. For the majority of countries, mortality is assumed to decline steadily between 2000 and 2050, the exception being the 45 countries highly affected by the HIV/AIDS epidemic for some of which mortality levels stagnate or even increase over the medium-term future because of AIDS. Only one mortality path is projected for each country and that path is combined with each of three different paths for future fertility to produce three projection variants known as the low, the medium and the high.
Assumptions about future fertility are made separately for three different categories of countries. The first is constituted of countries whose fertility in 1995–2000 was estimated to be below replacement level, that is, the level of fertility that would ensure that each woman has a daughter who survives to reproductive age. In countries with low mortality replacement-level fertility is about 2.1 children per woman. For countries that already have fertility below replacement level, future fertility is projected to remain below replacement level during most of the 2000–2050 period and to reach in 2045–2050 the total fertility level attained by the cohort of women born in the early 1960s .The second category of countries includes all those where the transition to low fertility has started but where fertility is still above replacement level. For those countries, fertility is assumed to reach replacement level (2.1 children per woman) on or before 2045–2050 and to remain at replacement level once it is reached. Lastly, for the third category of countries, those in which the transition to low fertility has not yet started, total fertility is assumed to decline at a rate of one child per decade starting in 2005 and no fertility change is assumed before that date. Given the high current
For countries lacking cohort data, the total fertility in 2045–2050 is set at 1.7 children per woman if total fertility in 1995–2000 is below 1.5 children per woman and at 1.9 children per woman otherwise.
levels of fertility that countries in this category have, most of them are projected to have fertility above replacement level in 2045–2050. This set of assumptions under-lies the medium projection variant. Low and high variants are produced by letting fertility be approximately 0.5 children below or above, respectively, that of the medium variant.
The assumptions about future fertility are based on an analysis of past fertility trends. Although, as mentioned above, most countries have already embarked on the transition to low fertility, as of 1995–2000 there was still considerable heterogeneity among countries in terms of the stage of the transition that they had reached. Using their 1995–2000 total fertility levels and information on past trends, countries were classified according to the stage of the transition they were in. As Table 5.1 indicates, in 2000 about 20% of the world population lived in the 43 countries that had experienced an early transition to low fertility, the large majority of which (35) are located in Europe. The group also includes Australia, Canada, Georgia, Japan, New Zealand, and the United States, as well as Argentina and Uruguay, the only two countries that experienced an early transition but whose fertility has remained well above replacement level. In contrast, all other early-transition countries have been experiencing below-replacement fertility levels, levels that have been maintained for at least a decade or two in most cases. It is this persistence of below-replacement fertility in the more-developed countries that provides the rationale for keeping future fertility below-replacement level for all countries that have a current fertility lower than 2.1 children for women. Table 5.1 shows that in addition to the early-transition countries there are 23 countries, accounting for about a quarter of the world population, whose fertility is also below-replacement level, the largest of which is China. For these countries as well, fertility is kept below replacement level during the projection period in the medium variant.
A further 52 countries are already fairly advanced in the transition to low fertility, with total fertility levels ranging from 2.1 children per woman to 4 children per woman. In the medium variant most of these countries are assumed to continue experiencing a decline of fertility but only until the level of 2.1 children per woman is reached. No further reductions of fertility are assumed thereafter. Because this group of countries accounts for nearly 40% of today’s population, assumptions about their future fertility have an important impact on long-term prospects for population growth and, given the experience of developed countries where below-replacement fertility is the rule, the issue of whether some of the intermediate fertility countries may reach below-replacement fertility in the future and maintain it thereafter is beginning to be considered. For some of the countries in this group, however, evidence regarding fertility trends in the recent past has shown that reductions have not been as fast as previously expected and suggest that stagnation of fertility levels may occur in the future. This is the case of populous countries such as Bangladesh and Egypt.
 Lastly, there are still 69 countries with fertility levels above 4 children per woman. Among them, 16 have not yet shown signs of embarking on the transition to low
In countries with fertility below replacement level, the low variant has a fertility 0.4 children per woman below the medium and the high variant has a fertility 0.4 children above the medium.

Table 5.1
Distribution of countries according to the stage they have reached in the transition to low fertility by major area, 1995–2000
Major area No transition Decline but  Decline to Decline to Decline to Decline to  Early transition,  Early transition  Total
TF still 54TF 53TF 42.1TF 3TF2.1 with  with “baby boom”,
2.1 TF 3TF2.1
Number of countries
Africa 15 21 8 6 2 1 0 0 53
Asia 1 10 3 11 11 12 0 2 50
Europe 0 0 0 0 1 3 0 35 39
Latin America and  0 0 7 3 14 7 2 0 33
the Caribbean
Northern America 0 0 0 0 0 0 0 2 2
Oceania 0 1 3 2 2 0 0 2 10
World 16 32 21 22 30 23 2 41 187
Percentage of population in each major area
Africa 20.7 43.2 12.4 22.3 1.3 0.1 0.0 0.0 100.0
Asia 0.5 6.3 0.8 37.9 10.9 39.9 0.0 3.6 100.0
Europe 0.0 0.0 0.0 0.0 0.4 0.9 0.0 98.7 100.0
Latin America and  0.0 0.0 8.7 3.7 76.4 3.4 7.8 0.0 100.0
the Caribbean
Northern America 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 100.0
Oceania 0.0 1.5 17.2 3.2 1.5 0.0 0.0 76.5 100.0
World 3.0 9.5 2.9 26.3 13.4 24.6 0.7 19.6 100.0
Source: United Nations (2001a). TF, total fertility, the average number of children a woman would have over her reproductive life if subject to the fertility rates of a given
period, 1995–2000 in this case.

fertility and a further 32 have fertility levels above 5 children per woman. Together, these two subsets of countries account for one-eighth of the world population. Even if these high-fertility countries proceed with the transition to low fertility at the average pace at which developing countries whose fertility has declined in the past 40 years achieved reductions, their populations will grow very rapidly. In fact, 12 of the 16 countries where the fertility transition has not yet started are projected to have a total fertility higher than 2.1 children per woman in 2045–2050, and the populations of all 16 countries combined are expected to grow at an average annual rate of nearly 2.8% during 2000–2050. In consequence, their share of the world population is expected to rise from 3% in 2000 to nearly 8% in 2050.
The heterogeneity characterizing countries both with respect to current fertility levels and in terms of expected future trends, results in trends at the world level that re ect a slowing down of the fertility decline in the medium variant, a more rapid reduction of future fertility in the low variant, and a slight rise followed by the stag- nation of fertility levels in the high variant (Fig. 5.4 and Table 5.2). In the medium variant, total fertility declines from 2.82 children per woman in 1995–2000 to 2.15 children per woman in 2045–2050, thus remaining above replacement level during the whole projection period. In the low variant, total fertility drops below replacement level in 2015–2020 and continues to decline so that by 2045–2050 it has reached 1.68 children per woman. In the high variant, fertility remains between 2.8 and 2.9 children per woman until 2025 and then declines slightly to reach 2.62 children per woman in 2045–2050. In all projection variants, fertility is lower in more developed regions than in less developed regions, but the tendency is for the fertility levels of those two groups to converge. Thus, whereas in 1995–2000 the difference in fertility levels between the more developed and the less developed regions is of approximately 1.5 children per woman – 1.57 children per woman vs. 3.1 children per woman, respectively – by 2045–2050 the largest difference is found in the high variant and amounts to just about 0.3 children per woman. That is, in all projection variants the fertility of less-developed regions declines significantly, whereas that of more- developed regions remains almost constant in the low variant and increases in the medium and high variants.
Among the countries in less-developed regions, those classified as least developed countries by the United Nations have, as a group, high levels of fertility (5.5 children per woman in 1995–2000). Although their fertility is expected to decline markedly during the next 50 years, by 2045–2050 the medium variant still has them exhibiting a total fertility of 2.5 children per woman, considerably above replacement level. In the high variant their fertility surpasses 3 children per woman and only in the low
The least-developed countries, as defined by the United Nations General Assembly in 1998, include 48 countries:
Afghanistan, Angola, Bangladesh, Benin, Bhutan, Burkina Faso, Burundi, Cambodia, Cape Verde, Central African Republic, Chad, Comoros, Democratic Republic of the Congo, Djibouti, Equatorial Guinea, Eritrea, Ethiopia, Gambia, Guinea, Guinea-Bissau, Haiti, Kiribati, Lao People’s Democratic Republic, Lesotho, Liberia, Madagascar, Malawi, Maldives, Mali, Mauritania, Mozambique, Myanmar, Nepal, Niger, Rwanda, Samoa, São Tomé and Príncipe, Sierra Leone, Solomon Islands, Somalia, Sudan, Togo, Tuvalu, Uganda, United Republic of Tanzania, Vanuatu, Yemen and Zambia. These countries are also included in the less developed regions.
Table 5.2
Total fertility estimates and projected values for the world, major areas and regions, 1950–1955 to 2045–2050
Major area 1950–1955 1975–1980 1995–2000 2000–2005 2020–2025 2045–2050
Low Medium High Low Medium High Low Medium High
World 5.01 3.90 2.82 2.49 2.68 2.87 1.96 2.39 2.83 1.68 2.15 2.62
More-developed regions 2.84 1.91 1.57 1.44 1.50 1.58 1.40 1.65 1.92 1.52 1.92 2.33
Less-developed regions 6.16 4.62 3.10 2.70 2.92 3.13 2.03 2.49 2.95 1.70 2.17 2.65
Least-developed countries 6.60 6.40 5.47 4.91 5.24 5.47 3.40 3.90 4.40 2.02 2.51 3.02
Africa 6.71 6.56 5.27 4.65 4.97 5.21 3.17 3.64 4.10 1.91 2.39 2.88
Asia 5.88 4.17 2.70 2.35 2.54 2.74 1.73 2.19 2.64 1.60 2.08 2.56
Latin America and the Caribbean 5.89 4.49 2.69 2.26 2.50 2.73 1.67 2.16 2.65 1.60 2.10 2.59
Northern America 3.47 1.78 2.00 1.76 1.90 2.09 1.61 1.93 2.32 1.68 2.08 2.48
Europe 2.66 1.97 1.41 1.31 1.34 1.38 1.26 1.47 1.69 1.41 1.81 2.20
Oceania 3.87 2.78 2.41 2.27 2.39 2.50 1.98 2.26 2.57 1.61 2.06 2.50
Source: United Nations (2001a).

variant do they reach replacement-level fertility. Countries in this group not only have
lagged behind other countries in the transition to low fertility but are also character-
ized by higher mortality levels, especially since many of them are highly affected by
the HIV/AIDS epidemic. Given the other social and economic constraints they face, the likelihood that they may progress rapidly through the demographic transition seems low. Even the moderate reductions of fertility projected under the medium variant may be hard to achieve. Most of the least-developed countries are located in Africa. Among all major areas of the world, Africa has today the highest fertility: 5.3 children per woman, nearly double the level in Asia or Latin America and the Caribbean. As Table 5.2 shows, although fertility in Africa has already declined with respect to the higher levels prevalent in the late 1970s, most of the continent is still at the early stages of the transition to lower fertility and both the medium and high variants assume that it will take the best part of the next 50 years for fertility in Africa to reach levels similar to those of Asia or Latin America today.
At the other end of the spectrum, Europe is experiencing very low levels of fertility, levels that are unprecedented in human history and that, if continued, will lead to a significant reduction of the population. According to past estimates, Europe’s fertility has been under replacement level since the 1970s and it is not expected to rise above replacement level in the near future. In fact, further fertility reductions are projected in all variants for the period 2000–2005 and only a small increase in fertility is projected by 2020–2025 in the medium and high variants. The rising fertility trend is maintained in both projection variants thereafter so that by 2045–2050, total fertility in Europe is projected to be 1.8 children per woman in the medium variant and 2.2 children per woman in the high variant. Only the low variant keeps total fertility in Europe declining steadily until 2025 and allows for a very small recuperation by 2050. Similar trends are followed by the fertility of Northern America, although the range of variation is smaller since fertility in that area has not fallen to the low levels observed in Europe. As for Asia, Latin America and the Caribbean, and Oceania, the low and medium variants project steady declines of fertility, whereas the high variant projects slight increases or a virtual stagnation of fertility levels until 2050.
Assumptions about future fertility are a key determinant of future population growth especially since they vary from one projection variant to the other. However, declining mortality also makes a significant contribution to population increases. Only one set of assumptions on future mortality trends is used to produce the various projection variants. Table 5.3 presents selected past estimates of life expectancy at birth and the assumed levels for that parameter in the future. At the world level, life expectancy increased from 46.5 years in 1950–1955 to 65 years in 1995–2000, a gain of 40%. Large reductions of mortality have been possible in the past because the interventions to control infectious and parasitic diseases are well known and of moderate cost. However, as infectious diseases come under control, the main causes of death shift to diseases that are harder to treat and that demand more costly interventions. Consequently, the higher the life expectancy already achieved, the more difficult it is to increase it further and some deceleration of the improvements of life expectancy is expected as higher levels are attained. In the case of the projected

Table 5.3
Estimated and projected life expectancy at birth and mortality decline index, world and major areas, 1950–1955 to 2045–2050
Major area Life expectancy at birth (in years) Mortality decline index
1950–1955 1975–1980 1995–2000 2000–2005 2020–2025 2045–2050 1950–1955 to  1995–2000 to  1995–2000 to
1995–2000 2025–2030 2045–2050
World 46.5 59.8 65.0 66.0 71.3 76.0 54 32 48
More-developed regions 66.2 72.3 74.9 75.6 79.3 82.1 61 39 55
Less-developed regions 41.0 56.8 62.9 64.1 69.7 75.0 56 32 48
Least-developed countries 35.5 45.3 50.3 51.4 60.6 69.7 33 33 51
Africa 37.8 48.3 51.4 51.3 59.6 69.5 32 29 50
Asia 41.3 58.4 65.8 67.4 73.0 77.1 62 37 51
Latin America and  51.4 63.0 69.3 70.4 74.3 77.8 62 31 45
the Caribbean
Northern America 68.9 73.4 76.7 77.7 80.7 82.7 68 39 53
Europe 65.7 71.5 73.2 73.7 77.7 80.8 51 35 51
Oceania 60.9 67.7 73.5 74.4 77.6 80.6 65 34 49
Source: United Nations (2001a).
The mortality decline index represents the increase in life expectancy actually attained as a percentage of the maximum possible increase over the period indicated, taking as maximum life expectancy that for Japan.

levels for the world population, it is expected that life expectancy will rise to 76 years in 2045–2050, an increase of 17% with respect to the level attained in 1995–2000.
To make comparisons between periods and among major areas on the basis of a more comparable metric, a mortality decline index was calculated by expressing the increase of life expectancy actually attained over a period as a percentage of the largest potential increase in life expectancy measured as the difference between the life expectancy in Japan (the country with the highest life expectancy) and the level a particular region had attained by the beginning of the period under consideration. Table 5.3 shows the values of the mortality decline index for three periods: 1950–1955 to 1995–2000; 1995–2000 to 2025–2030; and 1995–2000 to 2045–2050. Over the first period, which encompasses the second half of the 20th century, the index indicates that more-developed regions were somewhat more successful in reducing mortality in relative terms than less-developed regions, although less-developed regions recorded a greater absolute gain in life expectancy than more developed regions (22 years vs. 9 years). By 1995–2000, however, less developed regions still had a significantly lower life expectancy than more-developed regions: 63 years vs. 75 years. Among the less-developed regions, the least-developed countries made very small relative gains in life expectancy, achieving just 33% of the potential increase. By 1995–2000 their life expectancy still stood at a low 50 years. Once more, Africa experienced gains similar to those of the least-developed countries, achieving 32% of the potential rise in life expectancy by 1995–2000. The impact of the HIV/AIDS epidemic is largely responsible for the low gains made by Africa and the least-developed countries. In comparison, most of the other major areas fared better, achieving at least 62% of the potential rise in life expectancy. Only Europe recorded a lower overall increase, at 51% of the potential maximum, largely because of the stagnation or even the increases in mortality that have been experienced by Eastern European countries and, in particular, by the Russian Federation and other successor states of the former Soviet Union. In fact, Eastern Europe as a whole achieved only 24% of the potential rise in life expectancy between 1950–1955 and 1995–2000, with its life expectancy increasing by just 4 years over the period, from 64 years to 68 years.
For the future, relative gains in life expectancy are expected to be slightly lower over the next fifty years than over the past fifty, with most of the major areas achieving just about 50% of the potential maximum gain. More-developed regions are expected to make somewhat greater relative gains than less-developed regions, and the least-developed countries are expected to record fairly low relative gains by 2025–2030 but to improve their performance thereafter so that by the end of the projection period they are expected to attain 51% of the potential maximum increase in life expectancy. Yet, by 2045–2050 the least-developed countries are still expected to lag behind the rest of the developing world in terms of life expectancy (see Table 5.3). The low levels of the mortality index expected for the least-developed countries and for Africa by 2025–2030 are largely the result of the HIV/AIDS epidemic whose impact is projected to be greatest over the next two decades. Over the long run, how-ever, current projections assume that HIV prevalence will decline significantly so that the disease has a smaller effect in dampening gains in life expectancy after 2030.
Table 5.4
Life expectancy at birth in the 45 countries highly affected by the HIV/AIDS epidemic projected with and without
AIDS, 1990–2020
1990–1995 1995–2000 2000–2005 2005–2010 2010–2015 2015–2020
With AIDS 56.4 56.9 57.5 58.8 60.4 62.1
Without AIDS 57.7 59.8 61.7 63.5 65.2 66.7
Absolute difference 1.3 2.9 4.3 4.7 4.8 4.6
Percentage difference 2.4 5.2 7.4 8.1 7.9 7.4
Source: United Nations (2001a).

In fact, as Table 5.4 shows, when the 45 countries highly affected by the disease are taken as a whole, their life expectancy is expected to rise slowly between 2000 and 2020 even when the impact of HIV/AIDS is taken into account. Only when life expectancy with AIDS is compared with the one that would have been expected in the absence of the disease do its dire effects become evident. Thus, between 2000 and 2015 AIDS is likely to reduce life expectancy in the 45 most affected countries by about 8 years. Although this reduction will result in lower population growth in the highly affected countries than would have been expected without AIDS, outright reductions of population brought about by AIDS are generally not expected because most of the highly affected countries have and are expected to maintain moderate to high fertility levels relative to those of other countries.
In fact, as already shown in Fig. 5.3, the projected growth rates for the population of the world, though generally expected to decline over the next fifty years, are likely to remain well above the level they maintained before 1750. Furthermore, it is important to underscore that, whereas sustained low growth in the past was the result of high fertility coupled with very high mortality, in the future lower growth will most likely be universally attained by a combination of low fertility and low mortality. All the projection variants discussed above re ect this view. Even in the high variant, fertility remains at moderate to low levels which lead to substantial population growth only because they are higher than the level necessary for the long-term replacement of the population under conditions of low mortality. As Table 5.5 indicates, the high variant produces a world population of nearly 11 billion by 2050. However, the growth rates plotted in Fig. 5.3 suggest that the high variant may not represent the most likely path for future population growth at the world level since they show a marked change of trend with respect to the growth rates observed recently. Those for the medium and low variants appear to be more consistent with recent trends, at least over the next 10 or 20 years. Yet, whereas the medium variant produces a steadily increasing
The 45 highly affected countries are, in Africa: Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Côte d’Ivoire, Democratic Republic of the Congo, Djibouti, Eritrea, Ethiopia, Gabon, Gambia, Ghana, Guinea-Bissau, Kenya, Lesotho, Liberia, Malawi, Mali, Mozambique, Namibia, Nigeria, Rwanda, Sierra Leone, South Africa, Swaziland, Togo, Uganda, United Republic of Tanzania, Zambia and Zimbabwe. In Asia: Cambodia, India, Thailand and Myanmar. In Latin America and the Caribbean: Bahamas, Brazil, the Dominican Republic, Guyana, Haiti and Honduras. Except for Brazil and India, they all had an HIV prevalence among persons aged 15–49 of 1.9% or higher in 1999.
Table 5.5
Estimated and projected population by major area, development grouping and projection variant, 1950–2050
(in millions)
Major area 1950 1975 2000 2025 2050
Low Medium High Low Medium High
World 2519 4066 6057 7470 7937 8391 7866 9322 10 934
More-developed regions 814 1048 1191 1187 1219 1257 1075 1181 1309
Less-developed regions 1706 3017 4865 6283 6718 7135 6791 8141 9625
Least-developed countries 197 348 658 1112 1186 1255 1545 1830 2130
Africa 221 406 794 1275 1358 1434 1694 2000 2320
Asia 1399 2397 3672 4474 4777 5068 4527 5428 6430
Latin America and the Caribbean 167 322 519 644 695 746 657 806 975
Northern America 172 243 314 369 384 404 389 438 502
Europe 548 676 727 669 684 698 556 603 654
Oceania 13 21 31 39 40 41 42 47 53
Source: United Nations (2001a).

Table 5.6
Estimated and projected average annual population growth r ates, for the world and major areas, by projection
variant, 1950–2050
Major area 1950–1975 1975–2000 1995–2000 2000–2025 2025–2050
Low Medium High Low Medium High
World 1.91 1.59 1.35 0.84 1.08 1.30 0.21 0.64 1.06
More-developed 1.01 0.51 0.30 0.02 0.09 0.21 0.39 0.13 0.16
Less-developed 2.28 1.91 1.62 1.02 1.29 1.53 0.31 0.77 1.20
Least-developed 2.26 2.55 2.50 2.10 2.36 2.58 1.32 1.73 2.12
Africa 2.44 2.68 2.41 1.90 2.15 2.37 1.14 1.55 1.92
Asia 2.15 1.71 1.41 0.79 1.05 1.29 0.05 0.51 0.95
Latin America and  2.62 1.91 1.56 0.86 1.17 1.45 0.08 0.59 1.07
the Caribbean
Northern America 1.40 1.02 1.04 0.64 0.80 1.01 0.22 0.53 0.87
Europe 0.84 0.29 0.04 0.33 0.25 0.17 0.74 0.50 0.26
Oceania 2.09 1.44 1.37 0.96 1.09 1.22 0.36 0.66 0.96
Source: United Nations (2001a).
Population that reaches 9.3 billion by 2050, the low variant leads eventually to negative population growth (by 2045–2050) and produces a significantly lower population (7.9 billion in 2050). The implications of the different projection variants for future population growth are even more diverse at the level of development groups and major areas. Because of the diversity of past fertility and mortality levels, the populations of major areas are already growing at very different rates. Thus, whereas Africa’s population is increasing at 2.4% per year, Europe’s is decreasing at a rate of 0.04% (Table 5.6). The populations of Asia, Latin America and the Caribbean, and Oceania are still increasing at robust rates of 1.4% per year or higher, and even Northern America’s population is growing at a rate slightly above 1% per year, largely as a result of its moderately high fertility and net population gains through international migration. Owing to these varied experiences, population growth in the less-developed regions is nearly four times faster than in the more developed regions, and that differential is expected to become more accentuated in the future. Thus, during 2000–2025, less-developed regions are expected to grow 14 times faster than the more-developed regions in the medium variant and 7 times faster in the high variant, and according to the low variant, the population of more-developed regions will decline slowly, whereas that of less-developed regions will grow at a rate slightly above 1% per year. During 2025–2050, further reductions in growth rates for the more- and the less-developed regions are expected in all projection variants, but the differentials between them remain large. In the low and medium variants in particular, the population of more-developed regions is projected to decline during that period, whereas very substantial population increases are expected in the less-developed regions.
With regard to major areas, only Europe is expected to experience a reduction of the population in all the projection variants and Africa is expected to experience rapid population growth no matter which variant is considered. Differences between the variants become more marked the further one moves into the future so that by 2025–2050, the growth rates yielded by the high variant tend to be nearly 1% higher than those produced by the low variant. Consequently, while in the low variant most major areas are expected to experience rates of growth that approach zero, in the high variant the rates of growth are closer to 1%. The exceptions are Africa whose growth rate in the low variant is close to 1% and in the high is close to 2% and Europe whose rate of decline in the low variant is 0.74% and in the high variant is 0.26%.
The marked differences in expected growth rates for the major areas result in a redistribution of the population among them. The population of more developed regions, which is expected to be between 1.1 billion and 1.3 billion in 2050, will not be very different from that of today (1.2 billion), but there will be a redistribution of the population between the two major areas in the developed world. Thus, whereas the population of Europe is expected to decline from the 0.73 billion of 2000 to between 0.56 billion and 0.65 billion, that of Northern America will likely increase from 0.3 billion to somewhere between 0.4 billion and 0.5 billion. In the developing world, in contrast, large population increases are expected according to all projection variants. The population of the less-developed regions is expected to rise from 4.9 billion persons in 2000 to somewhere in the range of 6.8 billion to 9.6 billion, with the medium variant producing 8.1 billion. Among the major areas in the developing world, Africa is projected to record the largest relative increase, with its population doubling or tripling depending on the projection variant. Thus, its population passes from 0.8 billion in 2000 to 2 billion in 2050 according to the medium variant and might rise as high as 2.3 billion according to the high variant. The populations of Asia and Latin America and the Caribbean increase by about 50% according to the medium variant, so that the population of Asia passes from 3.7 billion in 2000 to 5.4 billion in 2050, and that of Latin America and the Caribbean rises from 0.5 billion in 2000 to

Table 5.7
Percentage distribution of the estimated and projected population of the world and
major areas, by projection variant, 1950–2050
Major area 1950 1975 2000 2050
                                                                                                                              Low Medium High
World 100.0 100.0 100.0 100.0 100.0 100.0
More-developed regions 32.3 25.8 19.7 13.7 12.7 12.0
Less-developed regions 67.7 74.2 80.3 86.3 87.3 88.0
Least-developed countries 7.8 8.6 10.9 19.6 19.6 19.5
Africa 8.8 10.0 13.1 21.5 21.5 21.2
Asia 55.5 58.9 60.6 57.5 58.2 58.8
Latin America and the Caribbean 6.6 7.9 8.6 8.4 8.6 8.9
Northern America 6.8 6.0 5.2 5.0 4.7 4.6
Europe 21.8 16.6 12.0 7.1 6.5 6.0
Oceania 0.5 0.5 0.5 0.5 0.5 0.5
Source: United Nations (2001a).

0.8 Billion in 2050. For Asia the low and high variants produce populations that are lower or higher by nearly 1 billion from that yielded by the medium variant. In the case of Latin America and the Caribbean, the equivalent difference is of the order of 150 million.
The changes in projected population size imply that by 2050 there will be a greater concentration of the population in the less-developed regions (Table 5.7). Thus, whereas in 2000 nearly 80% of the world’s population lived in the less-developed regions, by 2050 that proportion will rise to between 86 and 88%. Furthermore, among the major areas in the developing world a marked increase in the proportion living in Africa is expected: from 13% in 2000 to more than 21% in 2050. In contrast, the percentage living in Asia will decline slightly, from 61% to between 57 and 58%, and Europe’s share will decline markedly from 12% in 2000 to between 6 and 7% in 2050.
The further concentration of the population in the less-developed regions will not be accompanied by an increasing concentration in a few countries, although most of the populous countries of the world will be developing countries. As Table 5.8 indicates, 21 countries accounted in 1950 for three-quarters of the world’s population and 10 among them were located in the more-developed regions. By 2000, 24 countries were needed to account for the same proportion of the world’s inhabitants, but just eight were developed countries. By 2050, 29 countries are expected to account for 75% of the world population according to the medium variant with just five belonging to the more-developed regions. Furthermore, over the next fifty years India will likely displace China as the most populous country of the world and China’s share of the population will decline considerably, passing from 21% in 2000 to 16% in 2050 according to the medium variant. Indeed, given the size of China’s population and the fact that China’s fertility is projected to remain below replacement level after 2000 in the medium variant, China is expected to experience the largest population

Table 5.8
Countries accounting for 75% of the world population by order of population size, 1950, 2000, and 2050, medium variant
Country Population in  Cumulated  Country Population in  Cumulated  Country Population in  Cumulated
1950 (000) percentage 2000 (000) percentage 2050 (000) percentage
1 China 554 760 22 1 China 1275 133 21 1 India 1 572 055 17
2 India 357 561 36 2 India 1008 937 38 2 China 1 462 058 33
3 United States 157 813 42 3 United States 283 230 42 3 United States 397 063 37
4 Russian Federation 102 702 47 4 Indonesia 212 092 46 4 Pakistan 344 170 40
5 Japan 83 625 50 5 Brazil 170 406 49 5 Indonesia 311 335 44
6 Indonesia 79 538 53 6 Russian Federation 145 491 51 6 Nigeria 278 788 47
7 Germany 68 376 56 7 Pakistan 141 256 53 7 Bangladesh 265 432 50
8 Brazil 53 975 58 8 Bangladesh 137 439 56 8 Brazil 247 244 52
9 United Kingdom 50 616 60 9 Japan 127 096 58 9 Dem. Rep. of  203 527 55
the Congo
10 Italy 47 104 62 10 Nigeria 113 862 60 10 Ethiopia 186 452 57
11 France 41 829 63 11 Mexico 98 872 61 11 Mexico 146 651 58
12 Bangladesh 41 783 65 12 Germany 82 017 63 12 Philippines 128 383 59
13 Pakistan 39 659 67 13 Vietnam 78 137 64 13 Vietnam 123 782 61
14 Ukraine 37 298 68 14 Philippines 75 653 65 14 Iran  121 424 62
                                                                                                                                          (Islamic Republic of)
15 Nigeria 29 790 69 15 Iran (Islamic  70 330 66 15 Egypt 113 840 63
                                                                                      Republic of)
16 Spain 28 009 70 16 Egypt 67 884 67 16 Japan 109 220 64
17 Mexico 27 737 72 17 Turkey 66 668 69 17 Russian Federation 104 258 66
18 Vietnam 27 367 73 18 Ethiopia 62 908 70 18 Yemen 102 379 67
19 Poland 24 824 74 19 Thailand 62 806 71 19 Uganda 101 524 68
20 Egypt 21 834 74 20 United Kingdom 59 415 72 20 Turkey 98 818 69
21 Turkey 20 809 75 21 France 59 238 73 21 United Rep. of 82 740 70
                                                                                  22 Italy 57 530 74 22 Thailand 82 491 71
23 Dem. Rep. of  50 948 74 23 Afghanistan 72 267 71
the Congo
24 Ukraine 49 568 75 24 Colombia 70 862 72
                                                                                                                                            25 Germany 70 805 73
                                                                                                                          26 Myanmar 68 546 74
                                                                                                                                            27 Sudan 63 530 74
                                                                                                                                            28 France 61 832 75
29 Saudi Arabia 59 683 76
Source: United Nations (2001a).

Table 5.9
Countries experiencing the largest reductions or the largest increases of population in
2000–2005 and 2045–2050, medium variant
Country or area Population change in  Countr y or area Population change in
2000–2005 (thousands) 2045–2050 (thousands)
1 Russian Federation 4571.3 China 18 874.0
2 Ukraine 2269.8 Russian Federation 4370.8
3 Bulgaria 379.7 Japan 3255.4
4 Italy 365.0 Italy 2166.9
5 Kazakhstan 296.6 Ukraine 1937.2
6 Romania 287.4 Germany 1867.6
7 Hungary 247.0 Spain 1521.0
8 Belarus 203.0 Poland 799.5
9 Poland 178.5 United Kingdom 742.3
10 Germany 156.8 Republic of Korea 638.3
11 Georgia 137.8 Romania 538.1
12 Yugoslavia 77.7 France 508.7
13 Estonia 77.2 Cuba 331.1
14 Latvia 67.2 Bulgaria 303.9
15 Sweden 57.1 Kazakhstan 285.4
1 India 79644 India 31805
2 China 46231 Pakistan 17273
3 Pakistan 19090 Dem. Rep. of  15646
the Congo
4 Nigeria 15860 Nigeria 14824
5 Bangladesh 15113 Ethiopia 14586
6 Indonesia 13246 Yemen 11808
7 United States 12834 Uganda 9306
8 Brazil 10680 Bangladesh 9161
9 Dem. Rep. of  9258 United States 9137
the Congo
10 Ethiopia 8055 Niger 5828
11 Philippines 7352 Indonesia 5376
12 Mexico 7267 Angola 5349
13 Egypt 5922 Afghanistan 4990
14 Vietnam 5260 Somalia 4250
15 Iran  5036 United Rep.  4185
(Islamic Republic of) of Tanzania
Source: United Nations (2001a).

Reductions: during 2045–2050 alone its population is projected to decrease by nearly 19 million persons. At that time, 64 countries or areas are projected to experience negative rates of growth and therefore reductions of the population, up from the 27 expected to do so during 2000–2005. Table 5.9 shows the 15 countries expected to experience the largest reductions in population in 2000–2005 and 2045–2050. Note that, whereas the list for the earlier period includes mostly European countries and some of the successor states of the former Soviet Union, that for 2045–2050 also includes several countries from Eastern Asia (China, Japan, and the Republic of Korea) as well as Cuba.
Table 5.9 also shows the countries expected to record the largest increases of population in 2000–2005 and 2045–2050: they are mostly located in the developing world. India heads the list in both periods, although its population increment is expected to drop by more than half between the two periods. Only one developed country, the United States, is expected to experience large population increments partly as a result of the high numbers of immigrants projected to move to that country. In 2000–2005, countries from nearly all major areas are among those expected to experience large population increases, including two from Latin America (Brazil and Mexico) and three from sub-Saharan Africa (the Democratic Republic of Congo, Ethiopia, and Nigeria). By 2045–2050, in contrast, the countries with the highest population increases in absolute terms are most likely to be in sub-Saharan Africa (8 out of 15) or in the Indian subcontinent (Bangladesh, India, and Pakistan). Further- more, the largest increments in 2045–2050 are generally considerably smaller than those expected in 2000–2005. That is, as a result of the projected long-term reduction of fertility, expected population increments are expected to decline markedly even in the most populous countries over the next 50 years.
To complete the picture, let us consider the countries that are expected to experience the highest and the lowest rates of population growth during 2000–2050 (Table 5.10). The fastest growing countries tend to have relatively small populations that are projected to grow at sustained rates well above 2% per year over the period. As a result, their populations will increase dramatically, tripling in most cases but becoming five times larger than in 2000 in the cases of Liberia, Niger, and Yemen. The most populous country in this group, the Democratic Republic of Congo, is expected to see its population quadruple by 2050, rising from 51 million in 2000 to 204 million. Most of the countries with rapidly growing populations are among those that have not yet shown clear signs of embarking on the fertility transition or those whose fertility is still high. Even with the fairly large fertility reductions projected for the future, their fertility levels remain above those of other countries and have the potential of leading to very rapid and sustained growth if mortality levels keep on declining as projected.
At the other end of the distribution, the countries expected to experience the lowest rates of growth are among those whose populations are expected to decline during the projection period. Expected rates of population decline, even for the most rapidly declining populations, are considerably more moderate in absolute terms than the highest rates of population growth expected. Consequently, they lead in most cases to moderate reductions of population size over the next fifty years. Only two countries, Bulgaria and Estonia are expected to see their populations reduced by about half during 2000–2050. In most countries with rapidly declining populations the overall reductions over that period are expected to be in the range of 20–30%. The population of the Russian Federation, for instance, is projected to decline by about 28%, from 145 million in 2000 to 104 million in 2050. Sustained low fertility combined with mortality levels that are expected to decline more slowly than in other developed countries contribute to this outcome.
These results underscore the increasing heterogeneity of population dynamics that has been plain for the past century and that is expected to continue well into the

Table 5.10
Countries with the highest and lowest expected rates of growth during 2000–2050
(medium variant)
Country or area Population (thousands) Growth rate
2000 2050
Highest growth rate
1 Yemen 18 349 102379 3.44
2 Liberia 2913 14370 3.19
3 Niger 10 832 51872 3.13
4 Somalia 8778 40936 3.08
5 Uganda 23 300 101524 2.94
6 Angola 13 134 53328 2.80
7 Burkina Faso 11 535 46304 2.78
8 Dem. Rep. of the Congo 50 948 203527 2.77
9 Occupied Palestinian Terr. 3191 11821 2.62
10 Mali 11 351 41724 2.60
11 Congo 3018 10744 2.54
12 Chad 7885 27732 2.52
13 Oman 2538 8751 2.48
14 Afghanistan 21 765 72267 2.40
15 Solomon Islands 447 1458 2.36
Lowest growth rate
1 Estonia 1393 752 1.23
2 Bulgaria 7949 4531 1.12
3 Ukraine 49 568 29959 1.01
4 Georgia 5262 3219 0.98
5 Guyana 761 504 0.82
6 Russian Federation 145 491 104258 0.67
7 Latvia 2421 1744 0.66
8 Italy 57 530 42962 0.58
9 Hungary 9968 7486 0.57
10 Slovenia 1988 1527 0.53
11 Switzerland 7170 5607 0.49
12 Spain 39 910 31282 0.49
13 Gibraltar 27 21 0.49
14 Austria 8080 6452 0.45
15 Lithuania 3696 2989 0.42
Source: United Nations (2001a).

21st century as countries undergoes the demographic transition to low mortality and low fertility at different paces and facing different obstacles. Countries that have lagged behind in the transition to low fertility also tend to be those where mortality levels remain high. Many are already affected significantly by the HIV/AIDS epidemic and are therefore facing a more difficult task than in the past to ensure a longer life for most of their citizens. Whether they can muster the resources needed both to reduce mortality levels and to provide support for the reduction of fertility is still an open question. In the developed world, the maintenance of very low fertility levels is already producing reductions of population, especially in countries where mortality levels have stagnated or increased over the past two or three decades. In countries with economies in transition, achieving a steady reduction of mortality in future demands  important changes in access to health care, the improvement of health systems, and the implementation of programs to effect behavioral change at the societal level, interventions that are both demanding and costly. In addition, several of those countries are being faced with the spread of infectious diseases, such as tuberculosis and HIV/ AIDS, whose treatment is expensive and requires close supervision by health professionals. Under such conditions, it is unlikely that much effort will be expended in devising measures to promote higher fertility, especially since the evidence on their effectiveness is weak. Consequently, the likelihood of the continuation of recent trends, that is, of low fertility and only moderate gains in life expectancy, in the medium-term future is high. Lastly, varying rates of population aging will also lead to further het-erogeneity among the world’s population, since countries that embarked early on the transition to low fertility and those that have been experiencing below-replacement fertility will experience very marked aging whereas the populations of countries that are expected to continue growing at a rapid pace will experience a more moderate aging process. The dynamics of aging will be discussed in the next section.


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