Marital coitus across the life course

It remains unclear whether the frequency of marital coitus does in fact decline universally across the life course, what shape that decay normally takes, and what best accounts for it: increasing marriage duration, women's age or age of their partners. Using cross-sectional Demographic and Health Survey (DHS) data of 91,744 non-abstaining women in their first marriage, a generalized linear model is used to determine if there is a consistent pattern in the life course pattern of degradation in the frequency of marital coitus. Datasets were drawn from nineteen countries in Asia, Africa and the Americas. Use of very large samples allows proper disentangling of the effects of women's age, husband's age and marital duration, and use of samples from multiple countries allows consideration of the influence of varied prevailing fertility regimes and fertility-related practices on life course trajectories. It is found that declining coital frequency over time seems a shared demographic feature of human populations, but whether marriage duration, wife's age or husband's age is most responsible for that decline varies by country. In many cases, coital frequency actually increases with women's age into their thirties, once husband's age and marriage duration are taken into account, but in most cases coital frequency declines with husband's age and marital duration.     

Genetic structure of the Utah Mormons: isonymy analysis

Isonymy analysis is reported for a sample of 188,895 marriages extracted from the Utah Genealogical Database. Inbreeding rates estimated by isonymy are low, ranging from 0.005 for the earliest marriage cohort (1800-1809) to 0.0008 in the most recent cohort (1950-1959). The inbreeding values decrease considerably through time, but they are consistently higher than inbreeding values estimated from pedigrees. Several explanations are offered for this, including polyphyletism of surnames and the presence of Scandinavian patronyms in this population. Random isonymy between subdivisions is also compared with random kinship estimated from migration matrices. In terms of within-subdivision kinship, the two approaches yield similar results. However, the results are quite dissimilar for between-subdivision kinship. This reflects the recent and nonrandom settlement of Utah by different ethnic groups with different surname distributions. In later time periods, the correlations between the two types of kinship estimates increase, showing that migration patterns (which are strongly determined by geographic distance) exert an increasing influence on the distribution of surnames. Logistic regression is performed on a subset of marriages (n = 88,202), using isonymous vs. nonisonymous marriage as the dependent variable. The independent variables are year of marriage, geographic distance between husband's and wife's birthplaces, endogamous vs. exogamous marriage, and population sizes of husband's and wife's birthplaces. Year of marriage and geographic distance are shown to be significant independent predictors of isonymous marriage.     

Fecundability and husband's age

The effect of husband's age on the probability of conception is evaluated from World Fertility Survey data in five developing countries: the Ivory Coast, Ghana Kenya, the Sudan, and Syria. Proportional hazards models, which include wife's age, husband's age, marriage duration, union type, and post-partum exposure as covariates, are used to describe the monthly conception rate for second and higher-order birth intervals in which no contraception was used. With the exception of Syria, the resulting models indicate that the effects of male age are generally small in relation to the influences of marital duration and the age of the woman.     

Marriage structure and contraception in Niger

Analysis of the 1992 Niger Demographic and Health Survey showed that although roughly two-thirds of both polygamous and monogamous women approve of birth control, polygamous wives are less likely than monogamous wives to discuss family size or birth control with their husband or to plan on using birth control. The study suggests that characteristics of polygamous couples have caused polygamous women to be more resistant to birth control use than monogamous women. The polygamous women tended to be married to older men who had not gone to primary school and who desired more children than monogamous husbands. The influence of marital structure is not significantly associated with intention to use birth control when the husband's age and the wife's ideal number of children were controlled for in the multivariate logistic regression model suggesting that background social factors may be more influential. In fact, educational level and age at first marriage were significantly associated with attitudes towards birth control and also with marital structure.     

Reproductive success and occupational class in eighteenth-century Lancashire, England

Data from parish registers on 182 couples married between 1754 and 1772 in Lancashire, England, were used to compare lifetime reproductive success of farmers and craftsmen. Farmers were expected to be of higher average status and wealth than craftsmen; thus, these data were used to test the hypothesis that status and reproductive success were postively correlated in this society. Farmers raised a significantly higher mean number of children to age 21 than did craftsmen, although mean numbers of children born to farmers and craftsmen were not significantly different. The proportion of children surviving to age 21 was significantly higher for farmers than for craftsmen. For the 51 couples for which both husband's and wife's age at marriage were known, age differences were calculated. Mean age difference was 7.81 years for farmers and 1.95 years for craftsmen. Both husband's age at marriage and wife's age at marriage were positively correlated with childbearing span in the 51 cases. Of 112 marriages involving farmers, 53 (47.3%) involved premarital pregnancies; of 70 marriages involving craftsmen, only 16 (22.9%) involved premarital pregnancy.     

Duration between marriage and first birth and marital instability

This paper considers whether marital instability varies by the duration between marriage and 1st birth among ever-married white and black American women. Analysis of data from the June 1985 Current Population Survey suggests that the duration between marriage and 1st birth has a generally monotonic relationship with the probability of white women separating or divorcing from their 1st marriage; the relationship has remained relatively constant over time. For blacks, no consistent association is found between marital dissolution and the duration between marriage and 1st birth. Black women having a premarital conception and postmarital birth and those having their 1st birth during their 2nd year of marriage have a similarly high risk of dissolution. Conversely, blacks having their 1st birth 8-12 or 25-42 months after marrying have a low probability of dissolution. Childless women and those with premarital births generally has the greatest probability of marital disruption for whites. Racial differences may occur because blacks view the 1st birth and marriage differently than whites. That is, because blacks are much more likely to have premarital births and to have a shorter duration between marriage and 1st birth, blacks and whites in the same 1st birth interval category may be dissimilar and have different values resulting in a differential effect of the timing of the 1st birth on marital instability by race. Caution is needed when interpreting the pattern of association between delayed childbearing (and to a lesser extent, births occuring a few years after marriage) and marital instability. Results for whites were similar at each marriage duration and it is assumed delayed childbearing was not a result of marital instability. Marital instability was expected to have its strongest effect on the timing of the 1st birth during the 1st years of marriage. Marital instability may be partially responsible for the delaying of childbearing among blacks. However, blacks who delay but are married at 1st birth have a relatively low risk of separating or divorcing.     

Effects of polygyny and consanguinity on high fertility in the rural Arab population in South Jordan

Based on the authors' interview survey for 608 randomly selected women of the rural Arab population in the South Ghor district of Jordan, this paper examined the effects of polygyny and consanguinity on high fertility, which was recognized as natural fertility. The prevalence of polygynous and consanguineous marriages was 28.0% and 58.1%, respectively, largely reflecting the population's traditional marriage customs. The findings highlighted a significantly higher total marital fertility rate (TMFR) in the monogamous wives (10.5) than in the senior polygynous (8.1) and junior polygynous wives (8.6); the TMFR did not significantly differ among the wives of non-consanguineous, first-cousin and second-cousin marriages. The formation of polygynous marriage was decided by the husband, mostly as a result of his senior wife's infecundity or sub-fecundity, and the age of the husband at marriage to his junior polygynous wife was high in many cases, leading to a decline in this wife's fecundity.     

Continuing fertility transitions in a plural society: ethnic trends and differentials in Peninsular Malaysia

Fertility in Peninsular Malaysia has declined continuously from the late 1950s, reaching a total fertility rate of 3735 in 1983. All ethnic groups in Malaysia have contributed to this modern demographic transition but the rate of change has been most rapid for Chinese and Indians, Malay fertility having reached a plateau in the early 1980s. The effect of age structure, marital patterns and marital fertility (by parity) on the fertility declines for each ethnic community are analyzed. There has been a tendency, in each ethnic group, for the age distribution within the group of reproductive-age women to grow younger, reflecting the entry into the younger reproductive ages of the large birth cohorts of the 1950s and early 1960s. The effect of this on crude birth rates is hard to determine, because rising age at marriage and increasing use of contraception meant that fertility was increasingly concentrated in the more central reproductive ages. By the 1990s, the earlier declines in fertility will bring about a decline in the proportion of the total population made up of females in the main reproductive ages. After that point, further declines in fertility will be reflected in a sharper decline in the crude birth rate and hence the rate of population increase. Between 1947 and 1980, the age at marriage changed dramatically for females of all ethnic groups. The transition to higher age at marriage for Chinese was completed earlier, and since 1970 has risen by only a year. For Malays and Indians, the rise began later, proceeded faster and continued right up to 1980 when the medium ages at 1st marriage were Malays 22, Indians 23, Chinese 24 years. In 1980, Malay women on average were marrying 5 years later, and Indian women 6 years later than had their mothers' generation in 1947. The proportion never-married among Malay and Indian women aged 20-24 rose from 1/10 to 1/2 over this period; relatively greater changes are evident at ages 25-29. Other factors are the almost complete shift from parent-arranged to self-arranged marriages. Family size desired has decreased for all groups and the decline in breastfeeding has been offset by the sharp increase in the practice of contraception. Continuation of these trends would lead to replacement-level fertility for Malaysian Chinese and Indians by the year 2000. Malay fertility is likely to continue to decline but at a more moderate pace.     

Dynamics of Postmarital Residence among the Hadza

When we have asked Hadza whether married couples should live with the family of the wife (uxorilocally) or the family of the husband (virilocally), we are often told that young couples should spend the first years of a marriage living with the wife's family, and then later, after a few children have been born, the couple has more freedom--they can continue to reside with the wife's kin, or else they could join the husband's kin, or perhaps live in a camp where there are no close kin. In this paper, we address why shifts in kin coresidence patterns may arise in the later years of a marriage, after the birth of children. To do so, we model the inclusive fitness costs that wives might experience from leaving their own kin and joining their husband's kin as a function of the number of children in their nuclear family. Our model suggests that such shifts should become less costly to wives as their families grow. This simple model may help explain some of the dynamics of postmarital residence among the Hadza and offer insight into the dynamics of multilocal residence, the most prevalent form of postmarital residence among foragers.     

The relationship between legal abortion and marriage.

A study using the abortion-birth ratios for residents of each U.S. state for the second half of 1970 and for all of 1971 was done to determine if legal abortions reduced marriages. Data showed that trends were consistent with the hypothesis that a relationship exists between l egalized abortion-birth ratios and trends in crude marriage rates among states between 1967 and 1971 with reduction in crude marriage rates in the states with the relatively high abortion-birth ratios. Change in po licy on induced abortions may be responsible for the increased trend in the U.S. crude marriage rate from 1959-1970 and for its levelling off in 1971 and 1972. Analysis of data also suggested that there is a relation ship between less restrictive abortion policies and a decline in crude marriage rates. An estimation of the number of marriages postponed for at least one year following legal abortion indicated that about 1 abortion in 10 delays a marriage when all the decline in marriage rates were caused by increased abortions and when no legal abortions were subs titutes for illegal abortions. Results were obtained employing general measures for variables, but stronger relationships might be produced if more refined measures which consider race, age, parity, and marital status were introduced.     

Socioeconomic determinants of age at first marriage in Bangladesh

Using data from the 1976 Bangladesh Fertility Survey, multiple classification analysis was used to evaluate the effect of socioeconomic factors on age at 1st marriage. The independent variables considered were education, childhood and current residence, religion, work status before marriage, and husband's childhood residence, education, and occupation. Analysis was carried out for the total sample as well as for 3 birth cohorts of approximately equal size: 1) those born before 1940, 2) those born between 1940-50, and 3) those born after 1950. Of all the included variables, women's education has the strongest influence on the variation of age at 1st marriage. For all ever-married women, the mean age at marriage for women with primary education is 13.4 years, 0.9 years higher than for women with no education (12.5 years), and 1.2 years lower than for women with a high school education or beyond (14.6 years). Difference in means for cohorts indicate a gradually increasing influence of education on people's decision in marriage. Husband's education does not appear to be as important. Childhood residence has, directly and indirectly, a strong influence in marriage age. Among other factors, women's premarital work participation, as well as region and husband's occupation, are important. Since women's education, childhood residence, and work participation are the strongest socioeconomic variables affecting marriage age, the modernizing influences of education, urbanization, and female work participation should have an effect on the marriage pattern; this effect is consistent with that observed in other societies.     

Stable aggregate fertility in a time of family change: a decomposition of trends in American fertility, 1970-1999

Population-level birth rates in the United States were largely stable between 1970 and 1999. This stability contrasts with rapid change in marriage rates and fertility timing during the same period. In this article, I use decomposition techniques to analyze this seeming paradox. I decompose the general fertility rate into four components: age distribution, marital status, age-specific nonmarital fertility, and age-specific marital fertility. Absent other changes, declining time spent married would have led to substantial decline in fertility. Several factors combined to counterbalance these changes in marital behavior. Among white women in the 1970s and 1980s, marital fertility rates increased at older ages, consistent with a scenario in which women postponed both marriage and childbearing; increased nonmarital birth rates during this period were not a driving factor in overall fertility trends. Increased nonmarital fertility was more important in compensating for declining time spent married among African American women and among white women in the 1990s.     

Application of a marriage model in rural Bangladesh

The standard marriage model is evaluated with respect to its applicability in Bangladesh, so that reliable and consistent estimates of mean marriage age for females in Bangladesh can be made. The standard marriage model proposes that a person enters the marriage market and waits until marriage occurs. The distribution of age at entry into the marriage market is generally normal. The delays until marriage occurs are modelled as negative exponential distributions. In a population where marriage is universal, the standard schedule of 1st marriage frequencies developed by Coale and McNeil is a close approximation to the convolution of a normal curve and several exponential distributions G(x), the cumulative probability of marriage at age x. Since the standard distribution of age at 1st marriage is closely approximated by the convolution of a normal curve and several negative exponential distributions, the age at entry to the marriage market for females, and whether this is normally distributed, should be examined. 1 cross-sectional study in Bangladesh concludes that onset of menarche determines entry into the marriage market. The proportion of ever married females by single year of age which is available from cross sectional demographic surveys can be fitted to the Coale-McNeil model. Marriages in the rural areas of Bangladesh seem to follow the pattern of entering the marriage market at puberty, then waiting until actual marriage takes place. This model of entries and delays can also be fitted to cross-sectional data from rural Bangladesh. The use of the Coale-McNeil marriage model in rural Bangladesh is appropriate for estimating the mean age of marriage.     

Sex ratios at birth in a Micronesian atoll population

Abstract

The recent suggestion that typically masculinized sex ratios at birth in Micronesian populations may be related to a distinct “Micronesian pattern” of life‐course coital behavior is applied to data on the sex ratio of livebirths on Butaritari Atoll in Kiribati. The data show that sex ratios on Butaritari are highly masculinized and do not vary significantly with changes in maternal age. However, there is a discernible relationship between the length of closed intervals preceding male and female births. The lack of age‐related change in sex ratios in the Butaritari sample is inconsistent with ethnographic data regarding levels of marital coital activity in relation to increasing age and marriage duration. The Butaritari sex ratio data is argued to support the suggestion of a “Micronesian pattern,” although it is posed that further tests of this association are required.     

Response reliability of demographic data: a longitudinal study in Sri Lanka.

Response consistency was examined by linking the records of women interviewed in the 1982 Sri Lanka Contraceptive Prevalence Survey with records from the same individuals followed up 3 years later. Seventy-eight percent of women reported identical year of birth in the two surveys, but only 58% were consistent for age at marriage. Data on sterilisation and number of children born were highly reliable, but wives' reports on husband's age and education were relatively weak. Multivariate analysis of the effects of socioeconomic factors on consistency in age reporting confirms that education is the most influential factor related to consistency, followed by religion and husband's occupation.     

>For better or worse, till death us do part<--spousal age gap and differential longevity: evidence from historical demography

Based on a set of 2,371 family related entries dating from 1688 to 1921, the current study tried to verify longevity differentials due to interspousal age difference. For the purpose of the analysis, age-heterogamy was operationalized in terms of sample-specific marital age gap (3.2 years) with a standard deviation of 6.1 years. Based on this, five marriage groups were isolated. Female mean age at marriage experienced a slight increase over time, while the male mean at marriage decreased. This led to an appreciable narrowing of the spousal age gap. Age-homogamous unions were most prevalent in the lower socio-economic class (day-laborers, industrial workers) (p<0.01). In both husband-older and wife-older unions, the interspousal gap increased with marriage order. In accord with previous studies, mean age at death varied significantly by marriage group. Females, who married younger men, died later than females, who married older men. In contrast, male longevity was most depressed within age-similar marriages, while those who married older or younger wives displayed higher life spans. Overall, marriage to a younger spouse seemed to increase longevity prospects (p<0.05). These differentials were not exclusively a function of the marital age gap, but were affected by diverse confounders such as reproductive output and socio-economic status.     

Coital frequency and twinning. A comment.

The author comments on Bonnelykke et al's 1990 article on the coital rates of 390 mother of dizygotic twins (DZ), and finds that the data do not support the hypothesis that coital rates of mothers of DZ are higher than those of controls. The coital rates were 9.0 and 9.3/month respectively. Questions are raised as to the strength of the evidence, the sagacity of abandoning the hypothesis, or the probability of this sample size detecting differences. Cohen in 1977 hypothesized mean coital rates of DZ and control mothers and James in 1984 estimated rates of 16 and 15/month respectively. The coefficient of variation or the standard deviation divided by the mean has been found to be 2/3 regardless of the mean when age, parity and social class are controlled for. The harmonic mean of Bonnelykke's 2 sample sizes of 390 and 1206 is 589. Using Cohens Table 2.3.2 at 600 and at d=.1, the probability of detecting the hypothesized difference is .53 at the .05 level, which is impressive but not decisive evidence. Biological evidence supports the proposition of high coital rates at the time of conception and the birth of DZ twins. In double ovulation, oocytes are released usually at different times. The corpus luteum will have an inhibitory effect on the 2nd fertilization, but this condition must occur at 1st fertilization instantaneously. A plausible situation is the 1st fertilization is with an aging spermatozoa and the 2nd from a fresh ejaculate. Also supporting this notion is the fact of superfecundation, where fertilization occurs from spermatozoa from different ejaculates.     

Explaining Marital Patterns and Trends in Namibia: A Regression Analysis of 1992, 2000 and 2006 Demographic and Survey Data

Background

Marriage is a significant event in life-course of individuals, and creates a system that characterizes societal and economic structures. Marital patterns and dynamics over the years have changed a lot, with decreasing proportions of marriage, increased levels of divorce and co-habitation in developing countries. Although, such changes have been reported in African societies including Namibia, they have largely remained unexplained.

Objectives and Methods

In this paper, we examined trends and patterns of marital status of women of marriageable age: 15 to 49 years, in Namibia using the 1992, 2000 and 2006 Demographic and Health Survey (DHS) data. Trends were established for selected demographic variables. Two binary logistic regression models for ever-married versus never married, and cohabitation versus married were fitted to establish factors associated with such nuptial systems. Further a multinomial logistic regression models, adjusted for bio-demographic and socio-economic variables, were fitted separately for each year, to establish determinants of type of union (never married, married and cohabitation).

Results and Conclusions

Findings indicate a general change away from marriage, with a shift in singulate mean age at marriage. Cohabitation was prevalent among those less than 30 years of age, the odds were higher in urban areas and increased since 1992. Be as it may marriage remained a persistent nuptiality pattern, and common among the less educated and employed, but lower odds in urban areas. Results from multinomial model suggest that marital status was associated with age at marriage, total children born, region, place of residence, education level and religion. We conclude that marital patterns have undergone significant transformation over the past two decades in Namibia, with a coexistence of traditional marriage framework with co-habitation, and sizeable proportion remaining unmarried to the late 30s. A shift in the singulate mean age is becoming distinctive in the Namibian society.     

Birth spacing in Pakistan

Life table analysis was applied to data from the 1975 Pakistan Fertility Survey to identify child spacing differentials between population subgroups. Women in urban areas had shorter birth intervals than their rural counterparts from parities 1-6; only after parity 7 was this differential reversed. Similarly, women with some education had shorter birth intervals at the earlier parities than uneducated women. While overall family size is relatively homogeneous in Pakistan, women of more modern backgrounds seem to space their children more closely than traditional women. Age at marriage appears to play an important role not only in determining the length of the 1st interval, but also that of subsequent intervals. An unexpected finding was that ever users of contraception had distinctly more rapid spacing of their births than never users. The median interval to 1st birth was shortest in North West Frontier Province, but similar in Punjab and Sind. Multiple classification analysis revealed that some differentials in child spacing by education, residence, and province persisted even after other variables were controlled. Cohort of mother had an independent effect, with younger cohorts having shorter birth intervals. However, the variable that had the strongest effect on length of interval (aside from the 1st interval) was breastfeeding duration. It is likely that increasing urbanization and improved levels of education among women will lead to high levels of marital fertility associated with shorter birth intervals. Even though these trends tend to increase the age at marriage, they are associated with shorter durations of breastfeeding. In the longer term, greater use of contraception among women in the modern sector may partially counteract the fertility increasing effect of reduced birth intervals.     

Household extension and reproductive behaviour in Taiwan

The inflence of household type on reproductive behavior is examined for a national probability sample of Taiwanese women. Data were derived from a 1980 national household survey of the labor force in Taiwan, focusing on 10,624 couples. Reproductive variables include measures of current and prospective fertility as well as cumulative fertility. In spite of remarkable social and economic development over the past 3 decades, extended families are still widely found in Taiwan. Women in extended households have only slightly higher fertility preferences and current fertility than women in nuclear families once marital duration is controlled. Although women in extended households marry earlier and receive more family help with child care than women in nuclear families, such factors are no longer considered sufficient to produce major differentials in reproductive behavior. Residence and husband's class of work are the strongest correlates of whether a household is currently extended or nuclear. In general, the husband's characteristics are more strongly related to family type than the wife's. Findings suggest that preferences for smaller families and low fertility need not await a transformation to a nuclear family structue.