Past studies suggest that, across nations, the average cognitive ability of a population is negatively associated with income inequality; societies with higher average cognitive ability tend to have lower levels of income inequality. However, it is not clear why. This paper proposes that social transfers from the wealthy to the poor may be a major mechanism by which some societies achieve lower income inequality than others, because more intelligent individuals may be more likely to have a preference for such transfers. Publicly available societal-level data were analysed in a series of multiple regression models. The empirical results in this study replicate the earlier finding that societies with higher cognitive ability have lower levels of income inequality, but the association is entirely mediated by social transfers. Social transfers therefore appear to be the primary mechanism by which societies with higher levels of cognitive ability achieve lower income inequality.

This study examined the association between body composition, somatotype and socioeconomic status (SES) in Chilean children and adolescents by sex and school level (grade). The cross-sectional study was conducted on 1168 schoolchildren aged 6–18 years (572 males) from Valparaíso, Chile. Body composition, as assessed by percentage body fat (BF%) and somatotype, was evaluated using Ellis equations and the Heath–Carter method, respectively. The socioeconomic status of respondents was assessed using the ESOMAR survey. Obesity was defined as BF% ≥25 for boys and ≥30 for girls; ‘high endomorph’ somatotype was defined as a somatotype endomorph component (EC) of at least 5.5. Logistic regression analysis was used to assess the relationship between high adiposity and SES, potential confounding factors and school level. In females, the results indicated that the groups with lower SES had higher EC. At the 1st (youngest) school level (1–4th grades), males exhibited similar trends in their BF% and EC. High adiposity was associated with the female sex (BF%: OR=3.39; 95% CI 2.60, 4.41; high EC: OR=2.31; 95% CI 1.80, 2.98). In addition, low SES increased the risk of high adiposity compared with high SES (BF%: OR=2.25; 95% CI 1.40, 3.61; high EC: OR=2.19; 95% CI 1.37, 3.47). An association was observed between increased adiposity and lower SES, mainly in females, which indicates that females with low SES might be at greater risk of obesity.

Medical male circumcision has been recommended by the World Health Organization as part of a comprehensive approach to HIV prevention. Zimbabwe is one of the fourteen sub-Saharan countries that embarked on the Medical Male Circumcision (MMC) programme. However, the country has not yet met male circumcision targets. This paper examines the predictors of male circumcision in Zimbabwe. A cross-sectional survey was conducted on 784 men aged 15–35 years in Harare, Zimbabwe. Negative log-log logistic regression analysis was used to determine the predictors of male circumcision. The main predictors of circumcision were age, employment status, ever tested for HIV, approval of HIV testing prior to circumcision, knowledge about male circumcision and attitudes towards male circumcision. By and large, participants had good knowledge about male circumcision and viewed HIV prevention with a reasonably positive attitude. The identification of these predictors can be used to scale up the demand for male circumcision in Zimbabwe.

Although China’s family planning programme is often referred to in the singular, most notably the One-Child policy, in reality there have been a number of different policies in place simultaneously, targeted at different sub-populations characterized by region and socioeconomic conditions. This study attempted to systematically assess the differential impact of China’s family planning programmes over the past 40 years. The contribution of Parity Progression Ratios to fertility change among different sub-populations exposed to various family planning policies over time was assessed. Cross-sectional birth history data from six consecutive rounds of nationally representative population and family planning surveys from the early 1970s until the mid-2000s were used, covering all geographical regions of China. Four sub-populations exposed to differential family planning regimes were identified. The analyses provide compelling evidence of the influential role of family planning policies in reducing higher Parity Progression Ratios across different sub-populations, particularly in urban China where fertility dropped to replacement level even before the implementation of the One-Child policy. The prevailing socioeconomic conditions in turn have been instrumental in adapting and accelerating family planning policy responses to reducing fertility levels across China.

Globally, female sterilization is one of the most popular contraceptive methods despite concerns about quality of care for women who report being sterilized. In this study, informed choice among sterilized women was quantified using Demographic and Health Survey (DHS) data from 2000 to 2012 for countries in South Asia and Latin America. Three responses measured informed choice and knowledge about whether women were informed by a health worker or provider: that sterilization is permanent, the potential side-effects of sterilization and other methods of contraception. An ascending composite Method Information Index with scores ranging from 0 (women received no information) to 3 (women received information across all three indicators) was used. Using ordinal logistic regression analysis, the results indicated that women younger than 25 and older than 35 at the time of sterilization, and those at high parities, had lower odds of a high score on the index, while the opposite was true for women sterilized in the private sector in Latin America. Educated women in India had higher odds of a high score on the index, while the same was true for educated and wealthy women in Colombia. These findings indicate that not enough health care providers spend time informing women in South Asia and Latin America about different aspects of sterilization, and that there are specific groups of women that are more affected. There is an urgent need to improve quality of care within health systems providing sterilization for this very important and effective type of contraception.

The problem of overweight and obesity in children and adolescents has been noted in many different countries. The aim of this study was to evaluate the differences in the percentage occurrence of overweight and obesity in Polish children depending on the criteria used, and to evaluate the usefulness of the Polish national database. The study sample comprised 3405 children aged 5–14 years (1674 girls and 1731 boys) from the city of Kraków, Poland, in 2009–2010. The BMI of each child was calculated and classified as overweight or obese according to three different reference BMI cut-offs: the International Obesity Task Force (IOTF), the Centers for Disease Control and Prevention (CDC) and the Polish 2010 standard. To assess the statistical significance of the differences between these three applied reference datasets, a comparison of two proportions was performed and Cohen’s kappa coefficient calculated. The prevalences of overweight were 15%, 11.3% and 9.5% (IOTF, CDC, Polish 2010, respectively) among boys and 15.5%, 11.6% and 9.9% among girls. The prevalences of obesity were 3.3%, 6.1% and 5.5% (IOTF, CDC, Polish 2010, respectively) among boys and 3.4%, 6.3% and 5.7% among girls. The different methods used generally showed good agreement. Nevertheless the prevalence of overweight and obesity differed significantly depending on the criteria used. In conclusion, the creation and updating of national databases based on large, representative groups is justified and provides the best reference for regional data. However, in order to ensure the comparability of results with those from other countries, it seems advisable to use cut-offs based on international data as well.

The desire for children could be considered a reliable predictor of subsequent fertility. At the same time, the sex composition of surviving children, along with other demographic and socioeconomic factors, may affect a couple’s fertility desire and, therefore, their subsequent fertility. This study examined the impact of the sex composition of living children and a couple’s agreement on fertility desire on their subsequent fertility in India using data came from two rounds of nationally representative surveys: the India Human Development Survey (IHDS)-I (2004–05) and IHDS-II (2011–12). To understand which factors affect the chances of an additional pregnancy or childbirth, a random effects logistic regression model was applied to the panel data. It was found that the fertility desires of both marital partners were important in determining the chances of subsequent fertility. About 35% of the couples wanting to limit children had undergone pregnancy or childbirth, while 76% of the couples wanting more children had conceived or given birth to children. In the case of discordance between the spouses, subsequent fertility was found to remain intermediate between those agreeing to continue childbirth and those wanting to limit it. The findings also affirmed that child sex preference, specifically son preference, still persists in Indian society. More than 80% of the couples with only daughters in IHDS-I mutually wanted to have additional children, whereas in families that only had sons, the chance of a subsequent pregnancy was inversely associated with the number of sons. Strong patriarchal settings, combined with cultural and socioeconomic factors, affect the persistence of sex preference in India. Programmes aimed at increasing family planning use need to address son preference and should include components that promote the value of girl children.

Several studies report that women exposed to intimate partner violence (IPV) are less likely to use contraception, but the evidence that violence consistently constrains contraceptive use is inconclusive. One plausible explanation for this ambiguity is that the effects of violence on contraceptive use depend on whether couples are likely to have conflicting attitudes to it. In particular, although some men may engage in violence to prevent their partners from using contraception, they are only likely to do so if they have reason to oppose its use. Using a longitudinal follow-up to the Indian National Family Health Survey (NFHS-2), conducted among a sample of rural, married women of childbearing age, this study investigated whether the relationship between IPV and contraceptive use is contingent on whether women’s contraceptive intentions contradict men’s fertility preferences. Results indicate that women experiencing IPV are less likely to undergo sterilization, but only if they intended to use contraception and their partners wanted more children (Average Marginal Effect (AME)=−0.06; CI=−0.10, −0.01). Violence had no effect on sterilization among women who did not plan to use contraception (AME=−0.02; CI=−0.06, 0.03) or whose spouses did not want more children (AME=−0.01; CI=−0.9, 0.06). These results imply that violence enables some men to resolve disagreements over the use of contraception by imposing their fertility preferences on their partners. They also indicate that unmet need for contraception could be an intended consequence of violence.

Women’s decision-making autonomy has been poorly studied in most developing countries. The few existing studies suggest that it is closely linked to women’s socio-demographic characteristics and the social settings in which they live. This study examined Nigerian women’s perceived decision-making autonomy about their own health care using nationally representative data from the 2013 Nigerian Demographic and Health Survey. The study sample consisted of 27,135 women aged 15–49 years who lived with their husbands/partners. Responses to questions about who usually makes decisions about the respondent’s health care were analysed. Factors associated with women’s health care decision-making were investigated using logistic regression models. Only 6.2% of the women reported making their own decisions about health care. For most women (61.1%), this decision was made by their husband/partner alone and 32.7% reported joint decision-making with their husband/partner. Factors independently associated with decision-making by the woman included: geographical region, rural/urban residence, age, education, religion, wealth index, occupation, home ownership and husband’s occupation. A strong association between women making their own health care decision was seen with region of residence (χ2=3221.48, p<0.0001), even after controlling for other factors. Notably, women from the South West region were 8.3 times more likely to make their own health care decisions than women from the North West region. Factors that were significantly associated with joint health care decision-making were also significantly associated with decision-making by the woman alone. The study found that individual-level factors were significantly associated with Nigerian women’s decision-making autonomy, as well as other factors, in particular geographic region. The findings provide an important perspective on women’s health care decision-making autonomy in a developing country.

Societal gender inequality and a preference for male children has been shown to be detrimental to girls’ health. This is despite females’ innate biological advantage early in life. The negative effects of gender inequity on female health are most pronounced in resource-poor countries, where cultural norms supporting a preference for male children are strongest. However, most of what is known about gender inequality and child health comes from studies of singleton births. There is little evidence for how, or if, the disadvantages associated with gender bias and son preference extend to multiple births, a population inherently at risk for a number of health challenges. This analysis examines whether gender bias in health outcomes exists for twins. Data on live twin births from 38 Demographic and Health Surveys were compiled (n=11,528 individuals) and twins were categorized as girl/girl, girl/boy, boy/girl or girl/girl. Gender inequality was measured via the Gender Inequality Index. Multilevel logistic regression models examined associations between twin sex composition, gender inequality and eight outcomes of infant and child morbidity, mortality and mother’s treatment-seeking behaviours. Twin pairs containing girls had significantly lower odds of first-year mortality. Higher country-level gender inequality was associated with higher odds of reporting diarrhoea and fever/cough, as well as an increased odds of post-neonatal mortality. Results suggest that the biological advantage for females may be stronger than son preference and gender inequality in the first year of life. Understanding these relationships has the potential to inform efforts to curb the influence of gender preference on the health of female children in resource-poor settings.

Tubal ligation is the modal form of family planning among American women aged 30 and older. As the preference for tubal ligation over cheaper, lower risk and more reliable methods, such as vasectomy, has puzzled experts, a theoretical approach that explains this preference would be useful. The present study investigates the high prevalence of voluntary sterilization among American women from the perspective of life history theory, arguing that the trade-offs between investing in current and future offspring will favour tubal ligation when women cannot obtain reliable male commitment to future parental investment. Data came from the National Survey of Fertility Barriers (NSFB), a nationally representative survey of 4712 American women aged 25–45 conducted between 2004 and 2007. Four novel predictions of the prevalence of tubal ligation, drawn from life history theory, were developed and tested: 1) it is most common among unpartnered women with children, and least common among married women with children; 2) it is negatively correlated with age at first birth; 3) it is least common among highly educated women without children, and most common among less educated women with children; and 4) among women with two or more children, it is positively correlated with lifetime number of long-term partners. These predictions were tested using multivariate regression analysis. The first prediction was not supported: women with children were more likely to be sterilized, regardless of their marital status. The other three predictions were all supported by the data. The results suggest that trade-offs influence women’s decisions to undergo voluntary sterilization. Women are most likely to opt for tubal ligation when the costs of an additional child will impinge on their ability to invest in existing offspring, especially in the context of reduced male commitment.

A gender gap has been found in mathematics (boys outperform girls) that has prevailed across countries for many decades. Whether this gap results from nature or nurture has been hotly debated. Using the evidence of PISA 2003 and the gender equality index of 2003, some researchers have argued that an improvement in gender equality reduces the gender gap in mathematics. This study used five waves of country-level PISA data and, controlling for country fixed effects, found no evidence to support this argument. Furthermore, individual data for PISA 2012 and the multilevel data model were used. The conclusion drawn also does not support the argument. In fact, the relationship between gender equality and the gender gap in mathematics vanished after PISA 2003.

Zimbabwe has one of the worst HIV epidemics in the world. This study investigated data from two successive Zimbabwe Demographic and Health Surveys (ZDHS) conducted in 2005–06 and 2010–11. A random representative sample of 30,000 men aged 15–59 and women aged 15–49 was selected from the two surveys. The HIV prevalence was mapped with a flexible, coherent regression framework using a geo-additive semi-parametric mixed model. HIV indicator prevalence maps were constructed at the regional level, and at the administrative level relevant for policy design, planning and decision-making. Substantial regional variation was found, not only in the burden of HIV, but also in its risk factors. The results suggest that responses/policies should vary at the regional level to ensure that the often diverse needs of populations across a country are met and incorporated into planning the HIV response. The use of geographically referenced data in two successive ZDHS provides crucial new insights into the spatial characteristics of the HIV epidemic in Zimbabwe. In particular, it highlights the HIV heterogeneity across Zimbabwe, with substantial regional variation, not only in the burden of HIV, but also in its risk factors.

This study examined the relationship between orphanhood status, living arrangements and sexual debut. The study is important in the context of southern Africa, where a substantial number of children live apart from their parents because the parent is dead or living elsewhere, and where female adolescents face disproportionate sexual and reproductive health risks. Data for female adolescents were taken from Demographic and Health Surveys conducted in seven southern African countries. Unadjusted and adjusted hazard ratios of sexual debut were estimated using Cox Proportional Hazard models. The results from multivariate analyses showed that non-co-residence with biological parents was significantly associated with higher risk of sexual debut in five of the seven countries. Using pooled data, the results showed that father absence was associated with higher risk of sexual debut – whether the father was deceased or living elsewhere. Interventions to delay sexual debut among female adolescents should seek to promote father–adolescent co-residence and improve access to education.

This paper proposes a new empirical model for examining the relationship between obesity and school performance using the simultaneous equation modelling approach. The lagged effects of both learning and health outcomes were included to capture both the dynamic and inter-relational aspects of the relationship between obesity and school performance. The empirical application of this study used comprehensive data from the first five waves of the Longitudinal Study of Australian Children (LSAC), which commenced in 2004 (wave 1) and was repeated every two years until 2018. The study sample included 10,000 children, equally divided between two cohorts (infants and children) across Australia. The empirical results show that past learning and obesity status are strongly associated with most indicators of school outcomes, including reading, writing, spelling, grammar and numeracy national tests, and scores from the internationally standardized Peabody Picture Vocabulary Test and the Matrix Reasoning Test. The main findings of this study are robust due to the choice of obesity indicator and estimation methods.

Recent evidence indicates a rising trend in premarital sexual activity among young people in Iran. However, little is known about the extent to which young people’s sexual behaviours expose them to HIV and STI risks. This study aimed to assess HIV/STI-related sexual risk-taking behaviours (correlates and determinants) and HIV/STI risk perception among male university students in Tehran. A representative sample of male university students (N=1322) studying in government and private Tehran universities completed an anonymous questionnaire survey in 2013–14. Respondents were selected using two-stage stratified cluster sampling. About 35% of respondents had ever had premarital sex (n=462). The majority (about 85%) of the sexually experienced students reported having multiple sexual partners in their lifetime. More than half (54%) reported inconsistent condom use over the previous month. Despite this exposure to HIV/STI risk, the respondents had a very low level of HIV/STI risk perception. Only 6.5% were highly concerned about contracting HIV over the previous year, and an even lower percentage (3.4%) were concerned about contracting STIs in the near future. Early sexual debut (<18 years), studying in a private university, ever watching pornography and work experience were found to be significant predictors of having multiple sexual partners. Younger age at sexual debut, having one lifetime sexual partner and poor HIV knowledge were significant predictors of inconsistent condom use over the preceding month. HIV prevention programmes among Iranian youth need to focus on the postponement of first sex and enhancement of HIV/STI knowledge in the light of increasing access of young people to pornography.

The rapid economic growth in China has been accompanied by increases in internal migration as well as marital dissolution. Using longitudinal data from China Health and Nutrition Surveys covering over 19,000 individuals during 1989–2011, this study modelled the inter-relationships between internal migration, divorce and individual well-being, tackling conceptual and methodological aspects such as the joint determination of variables. First, random effects probit models showed that the migration periods of husbands and wives significantly increased their respective chances of divorce. Second, results from dynamic random effects models for self-reported health showed different effects of separation periods for husbands and wives; divorce did not significantly lower health status. Third, dynamic models for systolic and diastolic blood pressures showed significant effects of migration durations of husbands and wives; men had lower systolic blood pressure following divorce thereby indicating beneficial effects for unhappily married couples. The implications of the findings are discussed.

This study assessed the strength of the association between socioeconomic status (SES) and low birth weight (LBW) and preterm birth (PTB) in Southwestern Ontario. Utilizing perinatal and neonatal databases at the London Health Science Centre, maternal postal codes were entered into a Geographic Information System to determine home neighbourhoods. Neighbourhoods were defined by dissemination areas (DAs). Median household income for each DA was extracted from the latest Canadian Census and linked to each mother. All singleton infants born between February 2009 and February 2014 were included. Of 26,654 live singleton births, 6.4% were LBW and 9.7% were PTB. Top risk factors for LBW were: maternal amphetamine use, chronic hypertension and maternal marijuana use (OR respectively: 17.51, 3.18, 2.72); previously diagnosed diabetes, maternal narcotic use and insulin-controlled gestational diabetes predicted PTB (OR respectively: 17.95, 2.69, 2.42). Overall, SES had little impact on adverse birth outcomes, although low maternal education increased the likelihood of a LBW neonate (OR: 1.01).

Dietary diversity is associated with household or individual food availability and intake of nutrients from different food groups and is an important component of nutritional outcome. This study examined the Nutrient Adequacy Ratio (NAR) and the Mean Adequacy Ratio (MAR) of three dietary diversity indices and their relationship with the nutritional status of adolescents and adults in rural regions of two states in India, Wardha district in Maharashtra and Koraput district in Odisha, in 2014. Individual dietary diversity was calculated using 24-hour diet recall (FS24hr) data and household dietary diversity was measured with food frequency data using Berry’s index (DDI) and food scores (FSFFQ). The nutritional status of individuals was assessed using anthropometric indices. The diets in both locations were cereal dominated. It was observed that 51% of adolescent boys and 27% of adolescent girls had ‘thinness’ and stunting. The prevalence of undernutrition was higher among adult women (48%) than adult men (36%). The mean diversity indices were FS24hr of 8, DDI of 89–90 and FSFFQ of 64–66 in the two locations. The FS24hr was found to be positively correlated with the NAR of all nutrients while DDI and FSFFQ were correlated with seven and six nutrients, respectively. The DDI and FS24hr showed an association with MAR if the two locations were combined together. Sensitivity and specificity analysis showed that FS24hr gave more true positives than false positives and the area under the Receiver Operating Characteristic curve was 0.68, implying that this measure truly differentiates individuals having low dietary diversity with low MAR from those with low dietary diversity and a high MAR. All three measures of dietary diversity showed a linear association with the nutritional outcomes of adults, while in the adolescent group only DDI showed a relationship. It is concluded that 24-hour diet recall is a good measure for studying the relationship between dietary diversity and nutritional status in adults.

Over recent decades, economic living conditions have dramatically improved in South Korea, which now represents one of the most developed nations. At the same time, its twin in the North remains one of the poorest countries on earth. Thus, the Korean peninsula represents a unique historical experiment that allows for study of the effects of environment on human development under a variety of ceteris paribus cultural, genetic and climatic conditions. Previous studies comparing the biosocial performances of the two Koreas have focused on indicators such as weight, height, mid-upper arm circumference and age at menarche. The purpose of the present study was to investigate longevity based on the number of centenarians living in the two Koreas by drawing on censuses implemented around 1925 and 2010. The study found that North Korea had some 0.7 centenarians per one million persons in 1925, and this rate moderately improved to 2.7 around 2010. Conversely, rates skyrocketed in South Korea from 2.7 in 1925 to 38.2 around 2010. This suggests that the rate of centenarians in North Korea around 2010 corresponds to that of South Korea in 1925, suggesting a chronological lag in delayed human development of some 85 years. The prevalence of centenarians is fourteen times higher in contemporary South Korea compared with the North – broadly confirming previous biosocial studies on the two Koreas and two Germanies reporting improved human development in market-oriented systems compared with socialist ones.