The Demographic Transltlon One attempt to summarize an observed voluntary relationship between population growth and economic development is the demographic transition model. It traces the changing levels of human fertility and mortality presumably associated with industrialization and urbanization. The first stage of that replacement process-and of the demographic transition model-ls characterized by high birth and high but fluctuating death rates. As long as births only slightly exceed deaths, even when the rates of both are high, the population will grow only slowly.
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The Western Experience The demographic transition model was developed to explain the population history of Western Europe. That area entered a second stage with the industrialization that began about 1750. Its effects-declining death rates accompanied by continuing high birth rates-have been dispersed worldwide even without universal conversion to an industrial economy. The third stage follows when birth rates decline as people begin to control family size. When the birth rate falls and the death rate remains low, the population size begins to level off.
The classic demographic transition model ends ith a fourth and final stage characterized by very low birth and death rates. This stage yields at best only very slight percentage increases in population and doubling times stretch to a thousand years more. This extension of the fourth stage into a fifth of population decrease has so far been largely confined to the rich, Industrialized world-notably- Europe and Japan- but increasingly promises to affect much of the rest of the world as well.
The original transition model was devised to describe the experience of northwest European countries as they went from rural-agrarian societies to urban-industrial ones. Beginning about 1860, first death rates and then birth rates began their significant, though gradual, decline. This “mortality revolution” came first, as an epidemiologic transition echoed the demographic transition with which It is associated. A Divided World Converging The Demographic Equation Births and deaths among a region’s population-natural increases or decreases-tell only part of the story of population change.
The demographic equation summarizes the contribution made to regional population change over time by the combination of natural change (difference between
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births and deaths) and net migration (difference etween In-migration and out-migration). on a global scale, of course, all population change is accounted for by natural change. Population Relocation Immigration Impacts world Population Distribution Within the sections of the world generally conducive to settlement, four areas contain great clusters of population: East Asia, South Asia, Europe, and northeastern united States/southeastern Canada.
The East Asia zone, which includes Japan, China, Taiwan, and South Korea, is the largest cluster in both area and numbers. The four tors for almost one in five of the world’s inhabitants. The South Asia cluster is composed primarily of countries associated with the Indian subcontinent-Bangladesh, India, Pakistan, and the island state of Sri Lanka-though some might add to it the Southeast Asian countries of Cambodia, Myanmar, and Thailand. The four core countries alone account for another one-fifth, 21%, of the world’s inhabitants.
The South and the East Asian concentrations are thus home to nearly one-half the world’s people. Europe- southern, western, and eastern through Ukraine and much of European Russia- is the third extensive world population concentration, with another 12% of its inhabitants. Much smaller in extent and total numbers is the cluster in northeastern United States/southeastern Canada. The term ecumene is applied to permanently inhabited areas of the earth’s surface.
The ancient Greeks used the word, derived from their verb “to inhabit,” to describe their known world between what they believed to be the unpopulated, searing southern equatorial lands and the permanently frozen northern polar reaches of the earth. At the world scale, the ancient observation of habitability appears remarkably astute. The nonecumene, or anecumene, the uninhabited or very sparsely occupied zone, does include the permanent ice caps of he Far North and Antarctica and large segments of the tundra and coniferous forest of northern Asia and North America.
Population Density The term population density expresses the relationship between number of inhabitants and the area they occupy. Density fgures are useful, if sometimes misleading, representations of regional variations of human distribution. The crude density, or arithmetic density, of population is the most common and least satisfying expression of that variation. It is the calculation of the number of people per unit area of land, usually within the boundaries ofa political entity.
Another revealing refinement of crude density relates population not simply to total national territory but to that area of a country that is or may be cultivated, that is, to arable land. When total population is divided by arable land area alone, the resulting fgure is the physiological density, which is, in a sense, an expression of population pressure exerted on agricultural land. Agricultural density is still another useful variant. It simply excludes city populations from the physiological density calculation and reports the number of rural residents per unit of agriculturally productive land.
Overpopulation It is wise to remember that overpopulation is a value Judgement reflecting an observation or conviction than an environment or territory is unable adequately to support its present population. (A related but opposite concept of underpopulation refers to the circumstance of too few people to sufficiently develop the resources of a country or region to improve the level of living of its inhabitants. ) Overcrowding is a reflection not of numbers per unit area but of the carrying capacity of land- the number of people an area can support on a sustained basis given the prevailing echnology.
Urbanization More and more of world population increase must be accommodated not in rural areas, but in cities that hold the promise of Jobs and access to health, welfare, and other public services. As a result, the urbanization (transformation from rural to urban status according to individual state’s definition of “urban”) of population in Population Data Population Projections For all their inadequacies and imprecisions, current data reported for country units form the basis of population projections, estimates of future population size, age and sex composition based on current data.
Since projections are not predictions, they can never be wrong. They are simply the inevitable result of calculations about fertility, mortality, and migration rate applied to each age cohort of a population now living, and the making of birth rate, survival, and migration assumptions about cohorts yet unborn. Of course, the perfectly valid projections of future population size and structure resulting from those calculations may be dead wrong as predictions.
Because those projections are invariably treated as scientific expectations by a public that ignores their underlying qualifying assumptions, gencies such as the UN that estimate the population of, say, Africa in the year 2025, do so by not one but by three or more projections: high, medium, and low. Population Controls All population projections include an assumption that at some point in time population growth will cease and plateau at the replacement level. Without that assumption, future numbers become unthinkably large. Population pressures do not come from the amount of space humans occupy.
It has been calculated for example, that the entire human race could easily be accommodated within the boundaries of the state of Delaware. The problems stem from the food, energy, and other resources necessary to support the population and from the impact on the environment of the increasing demands and the technologies required to meet them. Rates of growth currently prevailing in many countries make it nearly impossible for them to achieve the kind of social and economic development they would like. Clearly, at some point population will have to stop increasing as fast it has been.
That is, either the self-induced limitations on expansion implicit in the demographic transition will be adopted or an equilibrium between population and resources will e established in more dramatic fashion. Recognition of this eventuality is not new. Thomas Robert Malthus (1766-1834), an English economist and demographer, put the problem succinctly in a treatise published in 1798: All biological populations have a potential for increase that exceeds the actual rate of increase, and the resources for the support of increase are limited. 1 . population is inevitably limited by the means of subsistence. . Populations invariably increase with increase in the means of subsistence unless prevented by powerful checks. 3. The checks that inhibit the reproductive capacity of populations nd keep it in balance with means of subsistence are either “private” (moral restraint, celibacy, and chastity) or “destructive” (war, poverty, pestilence, and famine. ) The deadly consequences of Malthus’s dictum that unchecked population increases reported throughout human history, as they are today. Starvation, the ultimate expression of resource depletion, is no stranger to the past of present.
When overpopulation of any species occurs, a population dieback is inevitable. The madly ascending leg of the I-curve is bent to the horizontal, and the J=curve is converted to n S-curve. The top of the S-curve represents a population size consistent with and supportable by the exploitable resource base. When the population is equivalent to the carrying capacity of the occupied area, it is said to have reached a homeostatic plateau. In animals, overcrowding and environmental stress apparently release an automatic physiological suppression of fertility.
In order to lift living standards, the existing national efforts to lower mortality rates had to be balanced by governmental programs to reduce birth rates. Neo-Malthusianism, as the viewpoint became known, as been the underpinning of national and international programs of population limitation primarily through birth control and family planning. Neo-Malthusianism has had a mixed reception. Asian countries, led by China and India, have in general- though with differing successes- adopted family planning programs and policies.
In some instances, success has been declared complete. Singapore established its Population and Family Planning Board in 1965, when its fertility rate was 4. 9 lifetime births per woman. By 1986, that rate had declined to 1. 7, well below the 2. 1 replacement level for developed countries, and the board was bolished as no longer necessary. A number of American economists called cornucopians expressed the view, beginning in the 1980s, that population growth is a stimulus, not a deterrent, to development and that human minds and skills are the world’s ultimate resource base.See More on Demography