Replacement Migration: A Questionable Tactic for Delaying the Inevitable Effects of Fertility Transition

This article critiques a recent U.N. Population Division report, Replacement Migration: Is it a Solution to Declining and Ageing Populations? The report explores the use of increased immigration to bolster future population size and change age distribution patterns in a group of developed countries. Fertility rate declines and lengthening life expectancies associated with demographic transition inevitably yield an aging population and a falling potential support ratio (PSR), a situation which some demographers and economists view with alarm. As the U.N. report itself suggests, replacement migration can only temporarily delay population aging and decline. These issues are ultimately better addressed through changes in retirement policy. Population projections should be used only with great caution in designing long-term demographic policy. In particular, some assumptions used to make the U.N. projections are questionable, and even minor changes in those assumptions would yield substantially different policy conclusions. Replacement migration also raises difficult environmental questions by moving large numbers of people from low to high per-capita consumption nations. Modest population decline, particularly in more developed countries, may have significant local and global environmental and climate policy benefits.

     

Effects of sterile insect releases on a population under predation or parasitism

Summary A continuous-time differential equation model was constructed which describes the population dynamics of a predator prey system in which sterile prey are released in a program designed to eradicate or reduce the prey population. It was found that the dynamics of the system behave quite differently when predators are present. Two conditions were found which have differing implications for the control program. If the predators still exist when the wild prey population declines to extinction, then the SIRM is assisted by the predators, sometimes to a considereble extent. If the predators decline to extinction before the wild prey population goes extinct, then the predators may or may not assist the SIRM depending on the parameters of the system. If the predators do assist the SIRM, then a potentially dangerous situation exists in which an explosion of the prey population could occur after the predators go extinct. Predator polyphagy would probably minimize this danger of an explosion since it would stabilize the predator population.     

Natural resource collection and desired family size: a longitudinal test of environment-population theories

Theories relating the changing environment to human fertility predict that declining natural resources may actually increase the demand for children. Unfortunately, most previous empirical studies have been limited to cross-sectional designs that limit our ability to understand links between processes that change over time. We take advantage of longitudinal measurement spanning more than a decade of change in the natural environment, household agricultural behaviors, and individual fertility preferences to reexamine this question. Using fixed effect models, we find that women experiencing increasing time required to collect firewood to heat and cook or fodder to feed animals (the dominant needs for natural resources in this setting) increased their desired family size, even as many other macro-level changes have reduced desired family size. In contrast to previous, cross-sectional studies, we find no evidence of such a relationship for men. Our findings regarding time spent collecting firewood are also new. These results support the “vicious circle” perspective and economic theories of fertility pointing to the value of children for household labor. This feedback from natural resource constraint to increased fertility is an important mechanism for understanding long-term environmental change.     

American education: the challenge of change

The American education system is being challenged to raise the academic achievement of students to prepare them for the jobs of the future. Yet many demographic, as well as economic and social factors, are making the task more difficult. Low birth rates, especially among non-Hispanic whites, along with high immigration rates, have increased the share of minority and non-English students in public schools. The rise in single-parent families has increased the number of poor students and migration from the cities to the suburbs has concentrated poor and minority students in inner city schools. These same children will make up a greater share of the future labor force. At the same time, the aging of the general population may lessen the commitment of homeowners- -whose taxes pay between 1/3 and 1/2 of education costs. The aging labor force may bring a shortage of qualified teachers, particularly in specialized subject areas. Poor and minority students generally have below average academic skills and are more likely to drop out of high school than non-minority students. However, the skills of American students rank below those of most other industrialized nations, calling into question the ability of Americans to succeed in an increasingly international economic system. How can schools be improved and minority student achievement be enhanced? Reforms of education finance systems, court-ordered integration, and stiffer requirements for teachers and for graduation from high school are among many attempts to meet the immense challenges faced by American schools.     

Is population growth a deterrent to development in the South Pacific?

Some have argued that population growth deters development, while others claim that population growth either aids development or has no significant effect on development. In a sample of South Pacific nations, population growth and size were found to be unrelated to economic development, defined as GDP per capita. However, when indices of quality of life or social development such as mortality, health services and education were used, population growth and size were found to be negatively related to these indices. If these “quality of life” indices are valued by nations, an argument may exist for policy support for family planning.     

World fertility and the women's situation]

In 1981, total number of childbearing women in the world reached 9.8 hundred million. Their socioeconomic status and fertility level are very important data for the study of women's liberation and population control. Facing limited natural resources and a constant growing demand, many nations are studying how to control the population growth and achieve a "zero population growth." In nations with a high GNP, such as Switzerland, West Germany, and France, fertility is low. On the contrary, countries in central and south Asia and most parts of Africa are the poorest economically, and their fertility rate has remained very high. Another factor which is related to the fertility level is the degree of women's participation in the labor market. In Europe and North America, the percentage of women's participation in economic activities is high, and fertility is low. In Latin America and Africa, fertility is high, and the percentage of women's participation in economic labor is low. From the above, we may conclude that promotion of women's participation in the labor market and better employment conditions will reduce fertility. Another 2 factors related to fertility are marriage age and birth control rate. Late marriage and the extensive use of birth control measures are effective methods for reducing fertility. All the above mentioned factors are closely related to the woman's educational background. If women receive a better education and find better employment opportunities, delay their marriage age, and take birth control measures, fertility will be reduced and the population growth will be under control.     

Negative population growth: how to go about it? (Letter to the editor)

It proves an interesting exercise to try to determine the effects of a national policy of government control developed on the basis of the need to conserve scarce resources, lessen environmental pollution, and to reduce the U.S. population to 1/2 of the 1970 figures within 100 years without increasing the risks of death. Let it additionally be assumed that in order to minimize the required reduction of fertility that there be no net migration. At the end of the reduction process, the stationary state in stable equilibrium might hopefully be achieved. If these are the goals, the process would include 1) reduction of the annual stream of births immediately to the number that would ultimately be required to sustain a population 1/2 as large as the present number and 2) smooth decline of the totals but with constituent age groups shifting drastically as the sharply reduced stream of births spreads upward through the span of life, with those 65 years and older making up 12% of the population. To obtain a fixed annual stream of births from sharply changing numbers of women of childbearing age would require rapid and drastic changes in the rates of childbearing. The same reduced population could be obtained from a system involving less drastic changes in the age composition, but these means would not be positive ones for older individuals. Both fertility and age distribution could move more smoothly if the mortality risks increased or with considerable emigration of the aged. Other means of reducing the population to 1/2 the present size within 100 years would create even more turbulence in the age distribution and rates of childbearing than those just discussed.     

Asian Americans: growth,change, and diversity

The 1980 US census counted 3.5 million Asian Americans, up from 1.4 million in 1970. Asian Americans made up just 1.5% of the total US population of 226.5 million as of April 1, 1980, but this was the 3rd largest racial or ethnic minority after blacks and Hispanics. Asians increased far more during the 1970s (141%) than blacks (17%) or Hispanics (39%). This Bulletin examines the characteristics of Asian Americans, how their numbers have grown, where they live, how different groups vary in age structure, childbearing, health, and longevity. It reports on the kinds of households Asian Americans form and how they fare with regard to education, occupation, and income. Asian Americans are now often perceived as the model minority. As a whole, they are better educated, occupy higher rungs on the occupational ladder, and earn more than the general US population and even white Americans. This Bulletin presents the 1st comprehensive look at many important facts about Asian Americans and how the groups differ. Special tabulations of data collected in the 1980 census are provided. The 1980 census data are the latest available to give a true picture at the national level of Asian Americans and the various groups among them. The Bulletin examines the current numbers of Asian Americans and how this population is defined. The major Asian American groups are Chinese (21%), Filipinos (20%), Japanese (15%), Vietnamese (21%), Koreans (11%), and Asian Indians (10%). Except for the latest-arrived Vietnamese, the fertility of the 6 groups is lower than the white average. The following areas are also discussed: mortality and health; families and households; education; Asian youth; employment; income and poverty; and future prospects.     

Declining world fertility: trends,causes, implications

This Bulletin examines the evidence that the world's fertility has declined in recent years, the factors that appear to have accounted for the decline, and the implications for fertility and population growth rates to the end of the century. On the basis of a compilation of estimates available for all nations of the world, the authors derive estimates which indicate that the world's total fertility rate dropped from 4.6 to 4.1 births per woman between 1968 and 1975, thanks largely to an earlier and more rapid and universal decline in the fertility of less developed countries (LDCs) than had been anticipated. Statistical analysis of available data suggests that the socioeconomic progress made by LDCs in this period was not great enough to account for more than a proportion of the fertility decline and that organized family planning programs were a major contributing factor. The authors' projections, which are compared to similar projections from the World Bank, the United Nations, and the U.S. Bureau of the Census, indicate that, by the year 2000, less than 1/5 of the world's population will be in the "red danger" circle of explosive population growth (2.1% or more annually); most LDCs will be in a phase of fertility decline; and many of them -- along with most now developed countries -- will be at or near replacement level of fertility. The authors warn that "our optimistic prediction is premised upon a big IF -- if (organized) family planning (in LDCs) continues. It remains imperative that all of the developed nations of the world continue their contribution to this program undiminished."     

Population,resources, environment: an uncertain future

This issue analyzes the economic and environmental consequences of rapid population growth in developing countries (LDC), the population decline in developed countries, the limits that life on a finite planet impose on economic and demographic expansion and progress, and the proper governmental response to promote the welfare of its current and future citizens. The links between population growth, resource use, and environmental quality are too complex to permit straightforward generalizations about direct causal relationships. However, rapid population growth has increased the number of poor people in LDC, thus contributing to degradation of the environment and the renewable resources of land, water, and nonhuman species on which humans depend. Demands of the rich industrial countries have also generated environmental pressures and have been foremost in consumption of the nonrenewable resources of fossil fuels, metals, and nonmetallic minerals. On the other hand, population and economic growth have also stimulated technological and management changes that help supply and use resources more effectively. Wide variations in the possible ultimate size of world population and accelerating technological change make future interrelationships of population, resources, and the environment uncertain as well as complex. Those interrelationships are mediated largely by government policies. Responsible governments can bring about a sustainable balance in the population/resource/environment equation by adopting population and development policies that experience has shown could reduce future population numbers in LDC below the additional 5 billion indicated in current UN medium projections. This coupled with proven management programs in both LDC and developed countries could brake and reverse the depletion and degradation of natural resources.     

Reproductive ideals and educational attainment among white Americans, 1943-1960

Abstract Would the persistent inverse relation between educational attainment and family size in the United States be removed if actual fertility were equal to ideal? Data on ideal family size from 10 national surveys among white Americans of both sexes (from 1943 to 1960) show that gradeschool level respondents have higher ideals than the more educated even when age, religious affiliation, and farm residence are used as controls. Comparison of these ideals with the actual family size or ever-fertile women in the United States indicates that, on the average, the actual family size of all major educational groups falls below the ideal, but the college-educated are furthest from their ideal. If this group lessened the gap between actual and ideal family size, the educational differential in fertility would decrease, but at the price of increasing the rate of population growth.     

On the relationship between population growth and economic development]

People are producers as well as consumers. If we look at only one side and ignore the other, we will be unable to reach impartial conclusions concerning the population problem. An obvious and close relationship exists between population growth and national economic development. If the two do not match each other, there will be numerous contradictory problems. For example, if the population grows too fast, serious social and economic problems will be created, such as a rise in the demand for living resources, an oversupply of the labor force, unemployment, and an insufficient availability of arable land, a shortage of public housing, more demand for health care and public transportation, and cultural and educational enterprises. In addition, a rapid population growth may cause more problems for the natural environment. As a result of overpopulation, the pressure on natural resources will be intensified and may therefore cause damage to the environment and create an ecological imbalance. All the above may bring very serious difficulties and obstacles to the advancement of socialism and modernized constructions. To avoid this, we must try to solve the population problem thoroughly and maintain a balanced relationship between the population growth and economic development.     

A mathematical model for resource allocation in population programs

The reduction of population growth rates through family planning programs is being attempted in many of the developing nations of the world. This activity lends itself aptly to mathematical modeling. Building from the well-known difference equation model of population growth, a model is constructed which integrates population dynamics, program activities, and resource consumption. The model may be used predictively to assess the outcome of various program activities. Alternatively, it may be used to determine the pattern of activities which yields the greatest reduction in births under the projected resource constraints. A further use of the model is the identification of the parameters to which predictions are most sensitive; such information provides valuable insights to those gathering the input data. The model is here applied to a family planning program currently in progress. An evaluation of the feasibility of that program’s goals is provided, as well as information on limiting resources, data sensitivity, and the most important ages for contraceptive acceptance.     

Lattice population dynamics for plants with dispersing seeds and Vegetative propagation

The population dynamics of plants in a lattice structured habitat are studied theoretically. Plants are assumed to propagate both by producing seeds that scatter over the population and by vegetative reproduction by extending runners, rhizomes, or roots, to neighboring vacant sites. In addtion, the seed production rate may be dependent on the local density in the neighborhood, indicating beneficial or harmful crowding effects. Two sets of population dynamical equation(s) are derived: one based onmean-field approximation and the other based onpair approximation (tracing both global and local densities simultaneously). We examine the accuracy of these approximate dynamics by comparing them with direct computer simulation of the stochastic lattice model. Pair approximation is much more accurate than mean-field approximation. Mean-field approximation overestimates the parameter range for persistence if crowding effects on seed production are harmful or weakly beneficial, but underestimates it if crowding effects are highly beneficial. Dynamics may show bistability (both population persistence and extinction) if the effect of crowding is strongly beneficial. If there is a linear trade-off between seed production and vegetative reproduction, the equilibrium abundance of the population may be maximised by a mixture of seed production and vegetative reproduction, rather than by pure seed production or by pure vegetative reproduction. This result is correctly predicted by pair approximation but not by mean-field approximation.     

The End of the Demographic Transition: Relief or Concern?

Demographic transition theory might seem to imply that, after a period of exceptional population growth resulting from the time lag between mortality and fertility declines, every population, and then the whole world population will stabilize and, consequently, no more acute population problems will appear. Does the claim, recently gaining credibility, that the end of the transition is at hand actually imply a stage without major population problems? Nothing is less sure. First, it is just a claim, the realization of which still entails a period of dramatically rapid population growth in some countries, especially the poorest. But more tellingly, the end of the transition is also the end of the paradigm on which we have been relying to understand and anticipate demographic changes. Nobody knows what might ensue later: How long and low can fertility fall? How long and high can life expectancy increase? How far can population aging go? As many questions without answer and probably as many problems whose size we cannot even imagine lie ahead.     

Estimating the completeness of reporting of adult deaths in populations that are approximately stable

An elaboration of Preston's (Preston and Hill, 1980) procedure for determining the completeness with which deaths are recorded in approximately stable populations is presented. Both the procedures of Preston and that of Brass are conventionally limited to mortality beyond early childhood, to mortality above age 5 or age 10. The method considered here is based on characteristics of stable populations, i.e., populations that have been subject for a long time to little variation in age-specific mortality schedules or in overall levels of fertility. The essential features of a stable population are maintained even if fertility has changed. This is the case as long as no strong trend in fertility existed more than 15 or 20 years before the date at which the population is observed. Recent changes in fertility may affect the structure of the population at adult ages, but the effect on estimates of completeness of death records can generally be kept within tolerably narrow limits. Prior to showing how explicit estimates of the relative completeness of recording of numbers of deaths and persons can be derived from counts of deaths and persons by age, it is noted that a life table for a stable population can be constructed directly from the recorded distribution of deaths by age, or from the recorded distribution of persons. The procedures described are applied to several different populations in order to illustrate the computational steps necessary to estimate the completeness of death records at ages above childhood in populations that are approximately stable.     

Planet earth 1984-2034: a demographic vision

In recognition of 1984 as the year of both Orwell's famous futuristic novel and the International Population Conference following up the 1974 World Population Conference, this Bulletin examines the current state of world population and presents the author's speculations on what it might be 50 years from now. World population, now close to 4.8 billion and growing at 1.8%/year, is being shaped by 3 demographic phenomena: prolonged below-replacement fertility in developed nations, perhaps partly in response to the reduced need for workers in the emerging information era; rapid growth despite failing fertility in developing nations, due to earlier rapid mortality decline; and rapid urbanization in developing nations and unprecedented migration from poor to better-off nations. The author's assumptions for nondemographic factors related to population change in the next 50 years are no world war, nuclear or otherwise; global resource adequacy; rapid scientific and technological progress shared equitably; and the demise of capitalism and communism and greatly increased economic aid from advanced to less advanced nations. For 2034 the author envisages nations divided into service/information societies (4% of global population) where immigration balances low fertility to prevent population decline; industrialized nations (38% of total), with fertility close to or at replacement level and growth slowing; developing nations (43%), in sight of replacement level fertility; and least developed nations, with still critical demographic problems but only 15% of the world population. Total population will be 8.03 billion, but growth will be down to 0.8%/year and global zero growth is possible in another 50 years. This relatively optimistic scenario for 2034 will only be possible if mankind acts to see that the stated nondemographic assumptions are borne out.     

Age structure,growth, attrition and accession: A new synthesis

This paper shows that each equation describing relationships among demographic parameters in a stable population is a special case of a similar and equally simple equation that applies to any closed population and demonstrates some implications of these new equations for demographic theory and practice. Much of formal demography deals with functions that pertain to individuals passing through life, or to a stationary population in which births of individuals are evenly distributed over time. These functions include life expectancy, probabilities of survival, net and gross reproduction rates, expected years spent in various states and the probability that certain events will occur in the course of life. The stable population model permits the translation of population structure or processes in a more general type of population, with constant growth rates, back into equivalent populations for a stationary population. The method for translation developed in this paper, requiring only a set of age-specific growth rates is even more general, applying to any population. Age specific growth rates may also be useful for performing reverse translations, between a population's life table and its birth rate or its age distribution. Tables of numbers of females by single years of age in Sweden are used to illustrate applications. Tables summarize the basic relations among certain functions in a stationary population, a stable population and any population. Applications of new equations, particularly to demographic estimation of mortality, fertility and migration, from incomplete data, are described. Some other applications include; the 2 sex problem, increment decrement tables, convergence of population to its stable form, and cyclical changes in vital rates. Stable population models will continue to demonstrate long term implications of changes in mortality and fertility. However, in demographic estimation and measurement, new procedures will support most of those based on stable assumptions.     

Energy and human evolution

Life on Earth is driven by energy. Autotrophs take it from solar radiation and heterotrophs take it from autotrophs. Energy captured slowly by photosynthesis is stored up, and as denser reservoirs of energy have come into being over the course of Earth's history, heterotrophs that could use more energy evolved to exploit them.Homo sapiens is such a heterotroph; indeed, the ability to use energy extra-somatically (outside the body) enables human beings to use far more energy than any other heterotroph that has ever evolved. The control of fire and the exploitation of fossil fuels have made it possible forHomo sapiens to release, in a short time, vast amounts of energy that accumulated long before the species appeared.By using extrasomatic energy to modify more and more of its environment to suit human needs, the human population effectively expanded its resource base so that for long periods it has exceeded contemporary requirements. This allowed an expansion of population similar to that of species introduced into extremely propitious new habitats, such as rabbits in Australia or Japanese beetles in the United States. The world's present population of over 5.5 billion is sustained and continues to grow through the use of extrasomatic energy.But the exhaustion of fossil fuels, which supply three quarters of this energy, is not far off, and no other energy source is abundant and cheap enough to take their place. A collapse of the earth's human population cannot be more than a few years away. If there are survivors, they will not be able to carry on the cultural traditions of civilization, which require abundant, cheap energy. It is unlikely, however, that the species itself can long persist without the energy whose exploitation is so much a part of itsmodus vivendi.The human species may be seen as having evolved in the service of entropy, and it cannot be expected to outlast the dense accumulations of energy that have helped define its niche. Human beings like to believe they are in control of their destiny, but when the history of life on Earth is seen in perspective, the evolution ofHomo sapiens is merely a transient episode that acts to redress the planet's energy balance.