Beyond Six Billion Forecasting the World's Population (2000) / Chapter Skim
Currently Skimming:
Introduction
Introduction
Pages 15-36
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 15... ...
Instead, world population has expanded much more rapidly than Malthus envisioned, growing from 1 to 6 billion over the past two centuries. Only very recently has population growth approached or actually reached zero in much of the industrial world and has rapid population growth begun to wind down in developing countries.
|
From page 16... ...
These agencies project population for individual countries, because such projections are useful for a variety of policy and planning purposes, and also because such a disaggregated approach is considered a good way to obtain regional and world totals. The updating of global and regional population projections every few years used to be a routine event that was ignored by much of the demographic community, in part because the numbers did not change much from one assessment to the next.
|
From page 17... ...
But if the number of children per woman in fact drops permanently below the replacement level in most countries, then even the newly revised population projections are still too high. Recognizing the importance of these and related demographic issues, the National Research Council responded to a request from a consortium of public and private sponsors by forming the Panel on Population Projections in 1998.
|
From page 18... ...
1 1900 1925 1950 1975 2000 2025 2050 FIGURE 1-1 World population size: Historical estimates and alternative projections. SOURCE: Data from United Nations (1999b)
|
From page 19... ...
and the World Bank expect growth to continue, with world population size reaching about 10 billion in the 22nd century. Such very long-range projections have considerable uncertainty and are difficult to evaluate, given that the historical record we can draw on is far shorter.
|
From page 20... ...
In contrast, in the industrial world (Europe and Russia, Northern America, Japan, and Australia and New Zealand) , population size is forecast to remain close to its current level of 1.17 billion.4 All four agencies agree that the rate of expected future growth between 1995 and 2050 will vary widely among the different regions of the 4This distinction between developing regions or countries and industrial regions or countries follows U.N.
|
From page 22... ...
anticipates overall growth in this time period to range from a high of 169 percent in Sub-Saharan Africa and 108 percent in the Middle East and North Africa to a low of 30 percent in East Asia. Trends in the two principal regions of the industrial world are also expected to diverge: the population of Northern America is expected to increase by 32 percent (from 0.30 to 0.39 billion people)
|
From page 23... ...
TABLE 1-3 Percent of population aged 65 and over for the world and major regions Region 1950 1995 2050 World total 5.2 6.6 16.4 Developing regions 3.9 4.7 15.0 Industrial regions 7.9 13.6 25.9 Sub-Saharan Africa 2.1 1.9 4.1 Middle East and North Africa 3.9 4.1 13.5 South and Central Asia 3.7 4.3 14.2 East Asia and Pacific 4.4 6.3 21.1 Latin America and Caribbean 3.7 5.1 16.8 Northern America 8.2 12.5 21.9 Europe and Russia 8.2 13.9 27.6 Source: United Nations (1999b)
|
From page 24... ...
In fact, the acceleration of population growth in Africa, Asia, and Latin America in the middle of the 20th century is largely a consequence of rapid declines in mortality in those regions. The future growth expected for the world and for most regions and countries will be partly due to continuing declines in mortality, but at least as important will be the extent to which fertility stays above the replacement level.
|
From page 25... ...
The assumption usually made is that average family size will eventually stabilize at the replacement level in Asia and Latin America before 2025 and in Africa before 2050. In countries where fertility is now below replacement, it is usually assumed that fertility will gradually rise back to the replacement level or slightly below it.
|
From page 26... ...
Latin America has reached mortality levels similar to those of the industrial world in the 1960s, and Asia is not far behind. Africa's mortality rates have remained the highest, resulting in a current life expectancy of 51 years.
|
From page 27... ...
That is, population size would decline for some time even were fertility to rise immediately to replacement level, mortality to remain at its current level, and net migration to stay at zero. The contribution of momentum to future population growth can be estimated by comparing a set of standard population projections with a set of hypothetical population projections for various regions of the world.
|
From page 28... ...
Given the standard assumptions, the world population will grow from 6.1 to 8.9 billion over the next half-century. Over half of this global population growth will be due to the momentum inherent in the current young age structure found in many parts of the developing world (Figure 1-3~.
|
From page 29... ...
but to continuing high levels of fertility and to declining mortality.7 HOW POPULATION PROJECTIONS ARE MADE There are various ways of projecting population size. The methodologies used range from the simple extrapolation of past trends to complex multiple-equation models involving dozens of demographic, socioeconomic, and environmental variables.
|
From page 30... ...
· Calculation of population projections. Once the initial population size, its age structure, and estimates of future component trends are all available, the calculation of the population size at future points in time is computationally straightforward (Shryock and Siegel, 1975~.
|
From page 31... ...
, these interruptions were generally attributed more to mistaken policy decisions than to demographic pressure (Dreze and Sen, 1990~. The rationale for ignoring environmental feedback is generally not discussed in the documentation accompanying current population projections.
|
From page 32... ...
Assumptions may then be reconsidered when necessary. Apparently, the major agencies making projections do not foresee strong pressures from future population growth that would significantly alter assumed trends in vital rates and migration, and the projections therefore do not explicitly incorporate environmental or other such factors.
|
From page 33... ...
For example, when in the 1970s China's leaders came to understand the implications of their population size and age structure for the country's future size, they decided to implement a policy of "later, longer, and fewer" for childbearing of all couples, later succeeded by a draconian one-child policy. These policies undoubtedly slowed the rate of China's population growth over the next 30 years, but their impact was not anticipated in the earlier population projections that triggered the policy decision in the first place.
|
From page 34... ...
Chapters 3 to 6 have the same general structure: they begin with an examination of past trends and available explanations for them and then review current projection procedures and their plausibility in view of the available scientific evidence. Chapter 7, which concludes the main text, discusses methods for assessing future uncertainty in projections and provides some estimates of prediction intervals for projected population.
|
From page 35... ...
Silberberg Frejka, T 1981 World population projections: A concise history.
|
From page 36... ...
U.S. Census Bureau 1999 World Population Profile: 1998.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.