The 1983 Somali Family Health Survey showed that polygamy and monogamy selected women with different social characteristics. Wives in polygamous unions were prone to be younger at first marital cohabitation and to have previous marital disruptions. Since a young age at first cohabitation and number of previous marriages have opposite effects on the cumulative fertility rate of women, the difference in this rate between wives in polygamous and monogamous unions vanished when both factors were controlled in a multivariate analysis.

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.

Nuñoa is a high altitude rural Peruvian community characterized by socioeconomic stratification and differential access to the market economy. Nursing practices and the effects of nursing are also stratified; this translates into a risk of menses at 12 months post-partum nearly seven times greater in wealthier than in poorer women.

Most nursing occurs in the morning, among those who practise on-demand breast-feeding. Nursing episodes are clustered into sessions; the amount of breast-feeding is regulated by varying the number of episodes per session rather than by changing the duration of suckling episodes or the frequency of sessions per hour. Thus, resumption of ovulation is not dependent on the variable spacing of nursing episodes or sessions. The components of nursing activity most likely to be responsible for variation in the duration of post-partum amenorrhoea in these nursing women are mean session duration and mean number of episodes per session.

The mean duration of morning nursing sessions is negatively associated with infant's age, reflecting the greater reliance of younger children on breast-milk. The mean duration of afternoon nursing sessions is positively associated with mother's age, independent of infant's age, possibly reflecting maternal age-related variation in milk production capabilities. Baby minding by older daughters may also help to explain variation in afternoon nursing.

Family planning knowledge, attitude and practice surveys typically assess respondents' reproductive attitudes and intentions to use contraception. Longitudinal observation of individual respondents nevertheless shows that such questions are not strongly predictive of subsequent behaviour. This study examines 3 years' data which show that a set of such responses to questions are nevertheless substantially superior in predicting behaviour than any single indicator. Thus statistical techniques which bring into account the apparent multidimensionality of contraceptive motivation can greatly improve upon the estimation of future practice of family planning in a population.

In 1984–85 a representative sample of 286 Danish women and 336 men aged 16–20 years were interviewed about their sexual debut. Seventy-four females (25·9%) and 101 males (30·1%) had not yet experienced sexual intercourse. A maximum likelihood estimation method was used to establish the age distribution at sexual debut. This takes into account knowledge of age at interview among the non-experienced respondents and of the few who did not report age at sexual debut. The median age at first sexual intercourse was close to 16·8 years for both females and males. This appeared to be a consequence of age at debut declining among women and remaining unchanged among males during the preceding 20 years.

Among the Kipsigis, a population of south-western Kenya who do not use contraception, age at menarche and age at last live birth could be determined for a cohort of post-menopausal women, through reference to clitoridectomy ceremonies that can easily be dated. While a woman's age at last live birth was strongly associated with the length of her reproductive lifespan, completed family size was better predicted by age at menarche. The demographic implications of variation in menarcheal age are discussed.

Humans in many societies are known to mate, or marry, assortatively for a number of characters such as eye colour, height, IQ and place of birth. In this assortment an element of active choice may be involved. It is not known whether this choice is genetic. Two models of human mate choice are examined in which both males and females can express a mating preference. In the first, ‘sexual’ preferences can be expressed for any phenotype not necessarily one's own; in the second, preferences are only expressed for an individual's own phenotype. The results of the examination indicate how much active choice would be needed to account for the observed correlations between human mates, and suggest whether human mating preferences are more likely to be sexual or assorting.

Birth history data from women in the 1975–76 Bangladesh Fertility Survey were used to search for intentions to replace dead children. The median intervals between successive births of orders (i) and (i + 1) were not shorter when some siblings of orders below (i) had died. Nor was the median duration between the death of a child and the first posthumous birth shorter when the dead child was a boy or when it was survived by fewer than two brothers. The median intervals were generally shorter when the mother lived in an urban rather than a rural area but this difference was attributable only to the shorter duration of breast-feeding by urban women. These results disputed the notions that the timing of births was deliberately quicker to replace a dead child, that attempts at replacement were sex-selective, or that child replacement intentions were stronger in urban than in rural populations.

This study examines the biological influence of infant death on subsequent fertility in three Asian countries—Indonesia, Nepal and Sri Lanka, comparing the birth interval between two consecutive births up to the sixth birth by survival status of the preceding infant among breast-feeding women not using contraception.

There is consistent evidence of biological influence in each of the three countries. Infant death shortens birth intervals by up to 30%, though its influence varies between the countries.

This paper investigates the association of early childhood mortality (between birth and second birthday) with ethnicity in Nepal, based on data from the 1976 Nepal Fertility Survey, which was part of the World Fertility Survey. The approach is through a series of hazard models, which incorporate ethnicity, year of birth, mother's illiteracy, father's illiteracy, rural-urban residence, region, sex, maternal age, survival of previous birth, previous birth interval, and breast-feeding as covariates. Ethnic differentials in early childhood mortality are not explained by the other socioeconomic and demographic covariates, except for a modest effect of illiteracy, but the remaining covariates explain a great deal of variability in early childhood mortality itself. Analysis using an improved specification of breast-feeding as an age-varying covariate indicates, on average, that breast-feeding, relative to not breast-feeding, reduces age-specific mortality risks during the first 2 years of life by 76%, a very large effect.

This analysis examines the relationship between length of preceding birth interval and risk of intrauterine growth retardation using data on Swedish infants from the 1973 World Health Organization study of perinatal mortality. Results of a multivariate logit analysis demonstrate that the lower than average mean birth weight of infants born after short birth intervals cannot be completely attributed to their shorter mean gestation length. Infants born after birth intervals of 12 months or less are 30% more likely to be small for gestational age (SGA) than infants born 18–59 months after the previous birth, even when the effects of maternal age and parity are controlled. The results obtained here do not support maternal depletion as an explanation for the association between short birth intervals and elevated risk of SGA, since there is no evidence of an attenuation of the risk of SGA with increasing length of interval in the under 18 month birth interval range.

Various studies have enquired into the influence of socioeconomic development or public health measures on life expectancies in less developed countries. Analysis of the effect of these two groups of factors upon life expectancy, using data for 95 less developed countries, indicates that mortality is primarily influenced by such socioeconomic development measures as urbanization, industrialization, and education, and secondarily by such public health measures as access to safe water, physicians, and adequate nutrition.