Socioeconomic determinants of fertility: selected Mexican regions, 1976-1977

Cumulative fertility is analyzed for 4 regions of Mexico, based on World Fertility Survey data of 1976-77; the state of Baja California, the Northwest region, the State of Jalisco, and the Northeast region. Based on stepwise regression methodology, the study compares results for 12 subsamples of married respondents, 3 age categories by 4 regions. The dependent variables are children ever born and children ever born in the last 5 years. Migration, urban, educational, and occupational variables are included as independent variables. Regression results reveal level of education is the major, and negative, influence on fertility. Other results include specific negative effects for prior occupation, size of place of residence, and childhood place of residence. Fertility effects appear different for migration origin and destination regions, but more similar for younger ages. Effects of migration on fertility are small. Mean fertility as measured by children ever born was 4.34 for the 1976-77 World Fertility Survey samples versus 3.69 for the Mexican census of 1980. Fertility varied somewhat by region with the highest and lowest values in Jalisco and the Northeast, respectively. Expected age-related changes in fertility were noted.     

Proximate determinants of fertility in Nigeria

Data from the 1981-82 Nigeria Fertility Survey (NFS) are used to identify the key proximate determinants of fertility in Nigeria. The patterns of their individual and collective effects are analyzed in a search for possible sources of fertility change. Exposure to the risk of childbearing through first marriage is found to be the most important proximate determinant of Nigerian fertility. Subsequent to marriage, fertility is determined mainly by breastfeeding and postpartum sexual abstinence. Where fertility shows significant socioeconomic variations, there are equally identifiable patterns of the impact of the proximate determinants which explain these differentials to a large extent. On a national scale, the observed patterns of the impact of the measured proximate determinants do not appear to suggest that Nigerian fertility is soon to experience a large decline.     

Determinants of fertility decline in China, 1981: analysis of intermediate variables.

This study examines the proximate determinants of fertility in China by making use of the data collected by the One-per-Thousand Sample Fertility Survey of 1982. The results indicate that the most important inhibitor of potential fertility is deliberate control. Its contribution to fertility change has been far greater than all other proximate determinants. The marital structure of the population is also an important factor, while lactational infecundability and induced abortion are relatively unimportant. Comparative results by using data from the In-depth Fertility Survey conducted in Shanghai Municipality, Hebei and Shaanxi Provinces in April 1985 agree well in the ranking of the four intermediate factors. The findings point to successful family planning program and government population policies, which propelled the fertility transition to a substantial degree. Further research needs and policy implications of the results of the study are discussed.     

Determinants of fertility decline in China, 1981: Analysis of intermediate variables

Abstract

This study examines the proximate determinants of fertility in China by making use of the data collected by the One‐per‐Thousand Sample Fertility Survey of 1982. The results indicate that the most important inhibitor of potential fertility is deliberate control. Its contribution to fertility change has been far greater than all other proximate determinants. The marital structure of the population is also an important factor, while lactational infecundability and induced abortion are relatively unimportant. Comparative results by using data from the In‐depth Fertility Survey conducted in Shanghai Municipality, Hebei and Shaanxi Provinces in April 1985 agree well in the ranking of the four intermediate factors. The findings point to successful family planning program and government population policies, which propelled the fertility transition to a substantial degree. Further research needs and policy implications of the results of the study are discussed.     

Individual fertility rate among minor tribal populations from Andhra Pradesh,India

Abstract

The Individual Fertility Rate (IFR), a measure of current fertility status in small and illiterate preindustrial societies, is estimated for five tribal populations from Andhra Pradesh, India. The Andhra tribes exhibit high individual fertility rates ranging between 49.62 ± 1.76 (Konda Dora) and 66.63 ± 3.16 (Manzai Mali) and fall in the high‐fertility category. The differences in IFR values between affinal and consanguineous couples are not significant. A direct positive relation between IFR and tribal hierarchy is observed with relatively higher IFR values recorded for socially higher‐ranked tribes in an ascending order from lower‐ to higher‐ranked groups.     

A stochastic version of the brass PF ratio adjustment of age-specific fertility schedules

Estimates of age-specific fertility rates based on survey data are known to suffer down-bias associated with incomplete reporting. Previously, William Brass (1964, 1965, 1968) proposed a series of adjustments of such data to reflect more appropriate levels of fertility through comparison with data on children-ever-born by age, a measure of cohort-specific cumulative fertility. His now widely-used Parity/Fertility or PF ratio method makes a number of strong assumptions, which have been the focus of an extended discussion in the literature on indirect estimation. However, while it is clear that the measures used in making adjusted age-specific fertility estimates with this method are captured with statistical uncertainty, little discussion of the nature of this uncertainty around PF-ratio based estimates of fertility has been entertained in the literature. Since both age-specific risk of childbearing and cumulative parity (children ever born) are measured with statistical uncertainty, an unknown credibility interval must surround every PF ratio-based estimate. Using the standard approach, this is unknown, limiting the ability to make statistical comparisons of fertility between groups or to understand stochasticity in population dynamics. This paper makes use of approaches applied to similar problems in engineering, the natural sciences, and decision analysis--often discussed under the title of uncertainty analysis or stochastic modeling--to characterize this uncertainty and to present a new method for making PF ratio-based fertility estimates with 95 percent uncertainty intervals. The implications for demographic analysis, between-group comparisons of fertility, and the field of statistical demography are explored.     

Socioeconomic status and fertility in rural Bangladesh

Using a unique set of birth registration data from the Demographic Surveillance System of the International Center for Diarrheal Disease Research, Bangladesh, for the period 1974-77, and socioeconomic information collected in the 1974 census, fertility was studied in relation to occupation, size of dwelling, number of cows and number of boats owned. The total fertility rate was found to vary between 6 and 6.5 except in the famine year of 1975. There was no consistent relationship between fertility and education of women. The age-specific fertility rates by religion show that Muslims had higher fertility at all ages in 1974 and 1977 and at older ages in 1975 and 1976. Overall, however, fertility of Hindus is consistently lower than that of Muslims, but the relative differences are under 10%. Fertility differentials by occupation showed that the household heads who were farm laborers had relatively lower fertility compared to other occupational groups, except for the year 1977 where the families of service holders were found to have relatively lower fertility. Women in households whose heads were businessmen or farmers (owning their land) had above average fertility. In 1974, households in the business occupational groups had, on average, 1 birth more than other households. Women in households with fishermen as heads had below average fertility in 1974 and 1975, but very high fertility in 1976 and 1977. Fertility levels differed according to the type of household in which the family resided. Nuclear families had below average fertility up to the age of 35 and above average fertility at the end of the reproductive age. In the 15-19 age group, augmented families had higher fertility each year examined. The association between dwelling place and fertility is positive each year, the relative differences in fertility between the groups being largest in 1974. Positive relations were found between economic status and fertility.     

Variation in wealth and educational drivers of fertility decline across 45 countries

Fertility decline in human populations is an inherent evolutionary puzzle with major demographic, socio-cultural and evolutionary consequences. The individual level predictors of fertility decline are numerous, but the way these effects vary by country and how they are causally mediated by other factors has received relatively little attention. Here we take a multilevel approach to compare similarities and differences in the primary predictors of contemporary fertility declines—wealth and education—across 45 countries in Africa, Asia, Central and South America, the Caribbean, and the Middle East using Demographic and Health Survey (DHS) data collected from 2003 to 2015. We use multilevel models to understand variation in the slopes of these predictors on fertility, and structural equation models to examine the causal pathways by which they take their effects, focusing on four mediating variables: local mortality and birth rates, women’s work status, and contraceptive use. We find that associations between wealth and fertility differ substantially across populations, while associations between education and fertility are consistently negative. The mediators also vary: community-level birth rates and women’s contraceptive use are important mediators between education, wealth and the number of children born across a wide variety of countries, but community-level mortality rates and women’s work status are not. We discuss our results in the context of different causal pathways that reflect cultural and biological evolutionary dynamics as simultaneous and interacting drivers of fertility decline.     

Recent evidence on trends and differentials in Bangladesh fertility

Recent data from Bangladesh reveal evidence of some fertility decline. Although fertility increased among younger age groups between 1975 and 1983, it was offset by a decrease in fertility in the older age groups, resulting in a slight overall decrease in total fertility in 1983. Fertility was lower among urban residents, educated mothers and contraceptive users than among rural residents, uneducated mothers and contraceptive non-users, respectively, particularly in 1983.     

Effects of racing on equine fertility

Racing and fertility are connected with each other in many ways. Stress and increased body temperature induced by racing may have negative effects on fertility, but on the other hand, high quality nutrition and management of racing horses may have positive effects. Fertility may also be genetically associated with racing performance. The analysed data consisted of Finnish mating records of Standardbreds (n=33,679) and Finnhorses (n=32,731), from 1991 to 2005, and the harness racing records of both mares and stallions. Fertility was measured by foaling outcome, and racing performance was measured by best time and number of races. We used racing results from the mating year and from the entire career, to study both short-term and long-term effects of racing on fertility. The analyses were conducted with a linear mixed model, where racing was fitted as a fixed factor. In a separate bivariate analysis we measured the genetic correlation of racing and fertility, applying a threshold model for the fertility trait. For mares, racing after the first mating or more than 10 times during the mating year diminished the foaling outcome. However, racing only before the first mating or 1-5 times during the mating year had positive effects on mare fertility. Stallion fertility did not suffer from racing during the mating year. The mares with the best career racing records had the highest foaling rates, but this was probably due to preferential treatment. The genetic correlation between best racing record and fertility was favourable but weak in the Finnhorse (-0.24±0.08), and negligible in the Standardbred (-0.15±0.11).     

Determinants of cumulative fertility in Kenya

This paper analyses the effects of age at first marriage, level of education, place of residence, marriage disruption, religion, contraceptive use, and work status on cumulative fertility in Kenya, using data from the 1977-78 Kenya Fertility Survey. Age at first marriage is the main determinant of cumulative fertility, but there are significant effects of level of education and marriage disruption. Place of residence is only significant for the Coast province. The implication of the findings is that to promote any real decline in fertility, emphasis should be placed on providing higher education and work opportunities for young women as an alternative to early marriage.     

Variation in the benefits of multiple mating on female fertility in wild stalk‐eyed flies

Polyandry, female mating with multiple males, is widespread across many taxa and almost ubiquitous in insects. This conflicts with the traditional idea that females are constrained by their comparatively large investment in each offspring, and so should only need to mate once or a few times. Females may need to mate multiply to gain sufficient sperm supplies to maintain their fertility, especially in species in which male promiscuity results in division of their ejaculate among many females. Here, we take a novel approach, utilizing wild‐caught individuals to explore how natural variation among females and males influences fertility gains for females. We studied this in the Malaysian stalk‐eyed fly species Teleopsis dalmanni. After an additional mating, females benefit from greatly increased fertility (proportion fertile eggs). Gains from multiple mating are not uniform across females; they are greatest when females have high fecundity or low fertility. Fertility gains also vary spatially, as we find an additional strong effect of the stream from which females were collected. Responses were unaffected by male mating history (males kept with females or in male‐only groups). Recent male mating may be of lesser importance because males in many species, including T. dalmanni, partition their ejaculate to maintain their fertility over many matings. This study highlights the importance of complementing laboratory studies with data on wild‐caught populations, where there is considerable heterogeneity between individuals. Future research should focus on environmental, demographic and genetic factors that are likely to significantly influence variation in individual female fecundity and fertility.     

A conceptual model for the identification, organization, and measure of influence of fertility policies and programs.

The fertility program of any government is the procedural action intended to effect the government fertility policy. There may also be unintended results of any fertility program. A conceptual model was designed to measure the effect of governmental action on fertility and to identify sociocultural factors that have the greatest influence on fertility. The model uses sociocultural variables as intervening variables between fertility programs and changes in actual fertility. The structural variables considered by the model are characteristics of the pattern of social order; the cultural variables consist of shared values and norms. Fertility trend analysis is effected by polynomial regression formulae. Puerto Rican data from 1946 to 1970 were used to test the proposed model. Analysis of the data indicated that emigration between 1940-1962 had little effect on national fertility. Governmental family planning programs, beginning in 1946, contributed to a sharp decline in fertility. It is recommended that the model be used with data from other countries to assess the effects of their family planning programs.     

Determinants of fertility in Nepal: applications of an aggregate model

Bongaarts aggregate model of the proximate determinants of fertility is applied to data from the 1976 National Fertility Survey in Nepal. Breastfeeding is shown to be the most important limiting factor, resulting in a reduction of about 6 children per woman. Decline in the duration of breastfeeding by 1/4 would increase fertility by 1 additional child per woman. The temporary separation of spouses due to migration is conjectured to be the 2nd most important fertility inhibiting factor, not explicitly accounted for in the standard model. Results are presented for the 3 major ecological regions, urban-rural residence and educational attainment of women. High nuptiality and virtually no contraceptive use in Nepal produce age-specific fertility rates very close to a natural fertility pattern. Total average interval between births is 36 months; about 18 months are solely due to breastfeeding, the remaining months to combined effects of gestation, waiting time to conception, intrauterine mortality and post-partum infecundability. As urbanization increases and pace of modernization becomes more pronounced, the duration of breastfeeding is susceptible to decline.     

Rural-urban differentials in marital fertility in four Muslim populations

An analysis based on data collected as a part of the World Fertility Survey program in 4 Muslim populations Bangladesh, Java, Jordan and Pakistan does not show a consistent pattern in rural-urban differentials in marital fertility. While no significant diiferential in current fertility by place of current residence is noticeable in Bangladesh and Pakistan, urban women in Jordan showed lower fertility than their rural counterparts. Cumulative fertility, when controlled for duration of marriage, was found to be higher in urban than in rural areas of Bangladesh and Pakistan, but no clear pattern emerged in Jordan. In Java, both current and cumulative fertility were higher in urban than in rural areas; urban women who had spent their childhood and were brought up in the urban environment showed, in most instances, higher fertility than the other residence groups. (author's modified     

Union instability and fertility in three Caribbean societies

This paper examines the relationship between sexual union instability and fertility in 3 English-speaking Caribbean societies--Guyana, Jamaica, and Trinidad/Tobago--using data collected in the World Fertility Program. There is usually a positive association between marital stability and fertility, the main reason being that marital instability causes periods of time in which a woman is not sexually active. High levels of divorce and marital separation are likely factors making for lower levels of aggregate fertility. To examine this relationship, this study used an index of cumulative fertility, the duration ratio, that controls for the biological effects of age, and age at 1st union was used as the dependent variable in a multiple regression analysis. The study demonstrated that despite many similarities between the 3 societies, there are also clear differences in terms of how membership in different types of sexual unions interacts with fertility. 1 main conclusion was that there is a positive association between the number of sexual unions and fertility, (in keeping with previous research on these societies). However, the factors were not uniform across the 3 societies. In Guyana marriage had the greatest effect on fertility while in Jamaica the 2 most unstable unions--visiting and common-law--had the greatest effect. In Trinidad/Tobago marriage and common-law had the greatest effect.     

Determinants of natural fertility in Sudan

The population of Sudan (North) is at a very early stage of fertility transition and experiences high, stable fertility at a close to natural level. The high observed fertility is found to be a function of the high proportion of married women and ineffective contraceptive procedures. The data used in this study were drawn from the 1979 Sudan Fertility Survey (SUDFS), in which 3115 ever-married women 50 years old from 12,028 households were interviewed. 90% of Sudanese women breast fed for at least 6 months and 80% for at least 12. The main inhibitor of fertility is perceived to be lactational amenorrhea averaging about 11.8 months, which is reported to be high, although among younger women the duration of amenorrhea is shorter due to earlier introduction of supplementary foods. An average of 5.2 months of postpartum sexual abstinence is evidenced, but this is shorter than the period of amennorhea, and therefore has no effect on the birth interval. Neither does marital instability or mean length of separation, which are both close to nonexistent. Sudanese women are comparatively very infecund. 22% gave birth within the 1st year of marriage, 62% within the 2nd, and 83% the 3rd. The proportion of ever-users of contraception is high (e.g. 15.4% among the 25-34 among category), but current use was low (8.1% for the same). The use of contraception is responsible for a reduction of 4.2% of the fertility per married woman. The duration of temporary separation between spouses, due to temporary or seasonal migration of husbands, and the pathological causes of high primary sterility, which contribute to the low fecundability, need further investigation.     

Control of fertility and fecundity of sheep by means of hormonal manipulation

The results of four experiments are presented in summary form. The data are considered in relationship to the improvement of the fecundity and fertility of the Australian ewe breeding flock. In the first, three commonly used methods of oestrous synchronization were examined and showed differences that are attributed to the different patterns of hormonal changes associated with the methods demonstrated. The second experiment looked at the use of active immunization against testosterone and concluded that this method can improve fecundity but not fertility. The third experiment, a group of five trials, studied the use of progestagen sponges and PMSG in anoestrous ewes as a means of inducing normal fertility. The extensive data produced in this experiment allowed the relationships between ovulation rate and fertility and between fertility and prolificacy (fecundity) to be examined. Fertility appeared greatest when the mean flock ovulation rate was about 2.5. At this ovulation rate prolificacy was also improved and a high proportion of twins were produced. We concluded that high fertility and low prolificacy (i.e. of 1.00) are an unlikely combination. In the final experiment the effect of post-mating hormonal supplementation on fertility was examined and a number of earlier reports were confirmed by showing that fertility can be improved with supplementary progesterone between days 10 and 25 post-mating. The effect appears to be modified by hormonal and nutritional factors.     

Matrilineal fertility inheritance detected in hunter-gatherer populations using the imbalance of gene genealogies

Fertility inheritance, a phenomenon in which an individual's number of offspring is positively correlated with his or her number of siblings, is a cultural process that can have a strong impact on genetic diversity. Until now, fertility inheritance has been detected primarily using genealogical databases. In this study, we develop a new method to infer fertility inheritance from genetic data in human populations. The method is based on the reconstruction of the gene genealogy of a sample of sequences from a given population and on the computation of the degree of imbalance in this genealogy. We show indeed that this level of imbalance increases with the level of fertility inheritance, and that other phenomena such as hidden population structure are unlikely to generate a signal of imbalance in the genealogy that would be confounded with fertility inheritance. By applying our method to mtDNA samples from 37 human populations, we show that matrilineal fertility inheritance is more frequent in hunter-gatherer populations than in food-producer populations. One possible explanation for this result is that in hunter-gatherer populations, individuals belonging to large kin networks may benefit from stronger social support and may be more likely to have a large number of offspring.     

Estimating tsetse fertility: daily averaging versus periodic larviposition

When computing mean daily fertility in adult female tsetse, the common practice of taking the reciprocal of the interlarval period (called averaged fertility) was compared with the method of taking the sum of the products of daily fertility and adult survivorship divided by the sum of daily survivorships (called periodic fertility). The latter method yielded a consistently higher measure of fertility (approximately 10% for tsetse) than the former method. A conversion factor was calculated to convert averaged fertility to periodic fertility. A feasibility criterion was determined for the viability of a tsetse population. Fertility and survivorship data from tsetse populations on Antelope Is. and Redcliff Is., both in Zimbabwe, were used to illustrate the feasibility criterion, as well as the limitations imposed by survivorship and fertility on the viability of tsetse populations. The 10% difference in fertility between the two methods of calculation makes the computation of population feasibility with some parameter combinations sometimes result in a wrong answer. It also underestimates both sterile male release rates required to eradicate a pest population, as well as the speed of resurgence if an eradication attempt fails.