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At least 19 recordsLinked to original sources
PubMed2005

Replacement fertility, what has it been and what does it mean?

Replacement fertility is a term commonly used by demographers when referring to levels of childbearing and yet is rarely explained. It is normally presented as being around 2.1 children per woman. Continued below replacement fertility in developed countries and fertility falling in developing countries has given the concept of replacement fertility a higher profile. This article explains how replacement level is calculated and explores the concept further. Past replacement fertility levels are calculated for England and Wales. A possible alternative definition of replacement is also presented. Simple projection scenarios are used to show the effect on population of below replacement fertility, and also of postponement of fertility. The importance and implications of below replacement fertility are discussed.

Adolescent↗
PubMed2001

A study of demographic changes under sustained below-replacement fertility in Hong Kong SAR.

The total fertility in Hong Kong SAR fell continuously below replacement in the past two decades and reached a level of 0.98 in 1998. The rate in 1981 was close to replacement at 1.93. In this paper the theoretical outcomes of long-lasting below-replacement fertility are identified with a view to gaining some analytical insight into the situation, where the population is experiencing such a striking demographic trend. In the absence of migration, Hong Kong SAR will see its population start to decline between 2008 and 2038, if the future course of fertility falls within these 'bounds'. Concurrently, the aging of population will be reaching unprecedented proportions. Should fertility remain at the present below-replacement level, i.e. the worse-case scenario, the proportion of population aged 65 years or older would increase to 44 per cent, and those aged under 15 years would decrease to six per cent, by 2048. As a result, the potential labour supply (those aged 15-64 years) would dwindle to only 50 per cent of the population, suggesting that there would be less than one person potentially working to support one dependent (who is likely to be a person aged 65 years or older). The socio-economic consequences of population aging are discussed. By analysing net immigration in the demographic process in the past, the way in which replacement migration would help alleviate the problem of population decline and population aging is also discussed.

Adolescent↗
PubMed1990

Immigration, below-replacement fertility, and long-term national population trends.

The long-term demographic effects of immigration on a population experiencing below-replacement fertility are studied by assuming that the size and age composition of the immigrant population do not change over time. The size of the first-generation immigrant population becomes stationary within a time period not greater than the human life span. Thereafter, the number dying equals the number entering over any given time interval. The stationarity of the native population, among which deaths exceed births, is maintained by the compensating number of births to the immigrant population. The limiting age distribution of the country's population, although stationary, may not decline monotonically with age and may look like a camel's back, with one or two humps.

Demography↗
PubMedDate not supplied

Evolutionary approach to below replacement fertility.

The large human brain, the long period of juvenile dependence, long life span, and male support of reproduction are the co-evolutionary result of the human niche based on skill-intensive techniques of resource accrual. The regulation of fertility under traditional conditions is based upon a co-evolved psychology and physiology where adjustments of investment in offspring depend upon the returns to skill and mortality hazards. When all wealth is somatic, the hormonal system controlling ovulation and implantation translates income into genetic descendants. In modern society the existence of extra-somatic wealth is a critical condition to which our evolved proximate physiological mechanisms do not respond. However, psychological mechanisms regulating parental investment in offspring quality may lead to greater and greater investment in own and offspring education, a smaller desired family size, a delay in the onset of reproduction, and a reduction in the total numbers of offspring produced. This delay in reproduction can cause many individuals to produce fewer children than desired because fecundity falls during the reproductive part of the life course. As more individuals in a society follow this pattern, more will fail to reach their desired family size. At the same time the effective use of birth control decreases the numbers of families producing more children than desired. Below replacement fertility can result. Predictions from this model were tested using data from the National Survey of Families and Households and the Albuquerque Men study.

Adult↗
PubMed1992

Immigrant's ages and the structure of stationary populations with below-replacement fertility.

A sustained regime of low fertility plus immigration yields an unusual kind of stationary population. The author demonstrates that all stationary populations have a common structure, and that the familiar replacement-level fertility population is the youngest among the many stationary populations corresponding to a particular life table. This finding has important consequences for policy because although fertility increase and immigration are equally effective at halting population decline, immigration is inferior as a means of rejuvenating low-fertility populations. In fact, an immigration-based policy could make a low-fertility population older rather than younger. The paper includes examples using U.S. and West German vital rates.

Adolescent↗
PubMed2003

The proximate determinants of the decline to below-replacement fertility in Addis Ababa, Ethiopia.

Between 1990 and 2000, the total fertility rate (TFR) in Ethiopia declined moderately from 6.4 to 5.9 children per woman of reproductive age. During the same period, the TFR in the capital city of Addis Ababa declined from 3.1 to 1.9 children per woman. Even more striking than the magnitude of this decline is that it occurred in the absence of a strong and effective national family planning program. In this study, the components of this fertility decline are identified using the Bongaarts framework of the proximate determinants of fertility. The results of a decomposition analysis indicate that a decrease in the age-specific proportions of women who are married, followed by an increase in contraceptive use are the most important mechanisms by which fertility has declined in Addis Ababa. Poor employment prospects and relatively high housing costs are likely factors that encourage couples to delay marriage and reduce marital fertility.

Abortion, Induced↗
PubMed1994

Replacement level fertility and future population growth.

'Replacement level fertility' is a technical term which seems almost self-explanatory. However there are some important qualifications which make it a more difficult concept than might be supposed. Also, the relationship between replacement level fertility and zero population growth is complicated. The article explains why this is so and thus why, although the United Kingdom's current level of fertility is below replacement level, population is projected to grow for the next thirty years.

Adolescent↗
PubMed1989

Does Australia's low fertility matter?

The author discusses the future effects of below-replacement fertility in Australia. "Continued below-replacement fertility would lead to a smaller maximum population, followed by population decline and an even older age structure. This paper argues that there is no need to increase the population and that a more mature age structure promises a number of benefits. Population growth imposes further costs on the already stressed natural environment and on the cities, and no economic benefits clearly offset these costs." Government policy to promote migration into Australia as a means of encouraging population growth is compared to the possible impact of a pronatalist policy. The author argues that social policies designed to reduce hardships faced by mothers are inherently desirable even if their demographic effects are uncertain.

Australia↗
PubMed1989

Outcome in 242 in vitro fertilization-embryo replacement or gamete intrafallopian transfer-induced pregnancies.

Two centers combined data on 152 in vitro fertilization embryo replacement and 90 gamete intrafallopian transfer generated pregnancies. The outcomes of the pregnancies with respect to abortion, ectopic gestation, and multiple gestation were evaluated independently by method and by center. Only with multiple gestation by center was a difference seen. Variables examined included estradiol levels, luteal phase support, maternal age, and prior reproductive history, and the number of eggs or embryos replaced.

Abortion, Spontaneous↗
PubMedDate not supplied

Prospects and programs for fertility reduction, 1990-2015.

What is the likelihood that each of the 37 developing countries with populations of 15 million or more in 1990 will reach replacement fertility by the year 2015? These countries have a combined population of 3.9 billion, 91 percent of the population of all developing countries. For this article, a composite index was used as the basis for predicting future levels of total fertility. The index was constructed from socioeconomic variables (life expectancy at birth, infant mortality rates, percent adult literacy, ratio of children enrolled in primary or secondary school, percent of the labor force in nonagricultural occupations, gross national product per capita, and percent of the population living in urban areas), total fertility rates for the years 1985-90, total fertility rate decline from 1960-65 to 1985-90, family planning program effort scores in 1989, and the level of contraceptive prevalence in 1990. Eight countries are classified as certain to reach replacement fertility by 2015, and an additional thirteen probably will also. Five countries are classified as possibly reaching replacement fertility, and eleven as unlikely to do so.

Birth Rate↗
PubMed1990

Long term demographic effect of a constant stream of immigration when the population is not reproducing itself.

The author describes the use of a model to investigate "the age composition of the stationary population resulting from a condition of below replacement fertility and a continuous stream of immigrants, the size of which for any age remain invariant over time.... We have shown that the number dying among [migrants] is the same as the number of them entering over any time interval, and that is precisely how their stationarity is maintained." The geographical focus is on developed countries that are experiencing below-replacement fertility levels. (SUMMARY IN FRE AND SPA)

Age Distribution↗
PubMed1996

Transition from high to replacement-level fertility in a Kerala village.

This paper uses a micro-approach to examine the motivation and processes of rapid fertility decline in a Kerala village. Fertility declined in the village substantially during the 1970s and continued to decline to reach replacement level at the time of study. The proximate determinants are postponement of marriage and extensive use of contraceptives. However, the changes in these factors were the result of changing socio-economic conditions. At the time of study the singulate age at marriage was 29 years for males and 23 years for females, higher than elsewhere in India. Delayed age at marriage was a combined effect of favourable attitudes to education and economic changes. Smaller families became advantageous because of decreasing agricultural opportunities, expanded education and mortality decline. Contraceptives were available with the implementation of the family planning program. Higher use of contraceptives can be attributed to favourable conditions resulting from socio-economic changes.

Adolescent↗
PubMed1994

Potential for fertility with replacement of hypothalamic gonadotropin-releasing hormone in long term female survivors of cranial tumors.

Dysfunction of the hypothalamic-pituitary axis presenting as hypogonadotropic amenorrhea is a common sequelae of treatment for cranial tumors with surgery and/or radiation. We hypothesized that the site of the defect in this condition is hypothalamic, rather than pituitary, in the majority of patients. Nine women with acquired hypogonadotropic hypogonadism after treatment with transphenoidal pituitary surgery (n = 3), transphenoidal surgery plus conventional radiotherapy (XRT; n = 1), hypothalamic surgery plus XRT (n = 2), or XRT with or without noncentral nervous system surgery (n = 3) underwent assessment of endogenous pulsatile LH secretion and a standard GnRH test followed by iv administration of a physiological replacement regimen of exogenous GnRH. A total of 25 cycles were completed at doses of 75 or 100 ng/kg.bolus. Ovulation occurred in 78% of patients, with all ovulatory patients who desired fertility becoming pregnant. The hormonal responses in these cycles did not differ from the patterns of sex steroids and gonadotropins in normal women. The response to pulsatile GnRH was not influenced by GH deficiency or PRL abnormalities. Of the two patients who failed to ovulate, there was no evidence of folliculogenesis in one, whereas the second consistently developed follicles, but proved incapable of mounting a LH surge despite adequate preovulatory estradiol levels. Both patients had a history of pituitary radiation and surgery. There was no consistent relationship between the results of GnRH testing and the pattern of pulsatile LH secretion. However, the only patient who failed to achieve folliculogenesis was the only patient without a FSH response to GnRH testing and an apulsatile baseline study. Hypothalamic GnRH deficiency is the etiology of hypogonadism in the majority of patients after treatment with hypothalamic or pituitary surgery or cranial irradiation. Therefore, exogenous pulsatile GnRH represents a physiological replacement therapy that completely restores normal gonadotropin dynamics, resulting in ovulation and fertility.

Adolescent↗