Women's subsistence strategies predict fertility across cultures, but context matters.

While it is commonly assumed that farmers have higher, and foragers lower, fertility compared to populations practicing other forms of subsistence, robust supportive evidence is lacking. We tested whether subsistence activities-incorporating market integration-are associated with fertility in 10,250 women from 27 small-scale societies and found considerable variation in fertility. This variation did not align with group-level subsistence typologies. Societies labeled as "farmers" did not have higher fertility than others, while "foragers" did not have lower fertility. However, at the individual level, we found strong evidence that fertility was positively associated with farming and moderate evidence of a negative relationship between foraging and fertility. Markers of market integration were strongly negatively correlated with fertility. Despite strong cross-cultural evidence, these relationships were not consistent in all populations, highlighting the importance of the socioecological context, which likely influences the diverse mechanisms driving the relationship between fertility and subsistence.

Aging, generational shifts, and energy consumption in urban China.

China is recognized as the largest energy consumer and is also the country with the largest and fastest-aging population. Ongoing demographic changes may reshape China's household-based energy consumption patterns because of the large gap in consumption behavior between the elderly and the young as well as varying attitudes toward the environment among generations. However, when the impact of China's aging population on energy consumption is projected, the heterogeneous cognitive norms of generations in the process of demographic transition are not well understood. In this study, we assessed the future impact of China's demographic transition on energy consumption using a proposed theoretical framework to distinguish between age and generational effects. Specifically, we used age-period-cohort (APC) detrended analysis to estimate age and generational effects based on China's urban household survey data from 1992 to 2015. The results indicated large differences in energy use propensity across ages and generations. The elderly and younger generations tended to be energy-intensive consumers, resulting in higher energy consumption in this aging society. Our results consequently show that future changes in China's elderly population will result in a substantial increase in energy consumption. By 2050, the changing consumption share of the elderly population will account for ∼17 to 26% of total energy consumption in the residential sector, which is close to 115 million tons of standard coal (Mtce). These findings highlight the need to interlace environmental education policies and demographic transitions to promote energy conservation behavior in children and youth for low-carbon, sustainable development.

The Impact of Multiple Births on Fertility: Stopping and Spacing in the United States During the Demographic Transition.

Multiple births strain mothers' and families' resources in ways that should highlight preferences for family size, birth spacing, and parity-dependent stopping behavior. Couples with surviving twins reach their target family size sooner than other couples and should be more likely to practice family limitation. Twins are also a greater burden on the mother's time and health, which could lead to postponing the next birth, even among couples who want additional children. We examine these hypotheses by analyzing families with twins in the 1900 and 1910 U.S. Censuses. Using reconstructed birth histories for more than 7 million women in the IPUMS full-count 1900 and 1910 datasets and event-history methods (Kaplan-Meier curves, cure models), we find clear evidence of family limitation following a multiple birth. Couples who had twins or triplets were more likely to stop childbearing, and those who continued having children delayed their next birth. Responses to multiple births were larger in groups previously identified as leaders in the transition to smaller families, and roughly one third of couples stopped after one or two children. We find no evidence that some groups relied primarily on birth spacing to reduce family size while others relied primarily on stopping.

The Fertility Transition in Sub-Saharan Africa: The Role of Structural Change.

Despite recent economic growth and reductions in child mortality in many African countries, the region has experienced a slow fertility transition. In this study, we explore whether the slow structural economic change on the continent can explain this discrepancy. We construct a unique panel dataset combining Demographic and Health Surveys and nighttime light intensity data (an indicator of industrialization) from 57 countries at the subnational region level over three decades to analyze the drivers of fertility transitions across low- and middle-income countries. Our results confirm that household wealth, reduced child mortality, and female primary education are crucial for fertility declines. However, our analysis also highlights the importance of indicators of structural economic change, including the share of labor in nonagricultural occupations, industrialization, the share of women with higher education, and the formalization of the economy. Our simulations suggest that if high-fertility countries in sub-Saharan Africa underwent structural economic transformations comparable to those of other low- and middle-income countries with low fertility rates, their fertility levels could fall by 1 to 1.6 children.

Are Rural Areas Holdouts in the Second Demographic Transition? Evidence From Canada and the United States.

A central premise of the first demographic transition theory is that demographic change would occur more slowly in rural than urban areas. Few studies, however, have investigated whether rural areas remain holdouts during the second demographic transition. To address this gap, this study (1) examines trends among rural and urban families in Canada and the United States over a 30-year period and (2) determines whether compositional differences in demographic, socioeconomic, and religious factors explain current differences between rural and urban families. We find that rural Canadian women continue to have, on average, 0.6 more children than urban women. However, rural families do not trail behind urban families on any other indicator of family change. In fact, rural women in both countries are now significantly more likely to cohabit and roughly 10 percentage points more likely to have children outside of marriage than urban women. These differences are largely explained by lower levels of education and income among rural American women and fewer immigrants in rural Canada. Examining family change through a rural-urban lens fills important empirical gaps and yields novel insights into current debates on the fundamental causes of ongoing family change in high-income countries.

Intergenerational Clustering of Under-Five Mortality: A Cohort Perspective in Low- and Middle-Income Countries.

A burgeoning demographic literature documents the exceedingly high rates at which contemporary cohorts of women across the Global South experience the death of their children-even amid historic declines in child mortality. Yet, the patterning of maternal bereavement remains underinvestigated, as does the extent to which it replicates across generations of the same family. To that end, we ask: Are the surviving daughters of bereaved mothers more likely to eventually experience maternal bereavement? How does the intergenerational clustering of maternal bereavement vary across countries and cohorts? To answer these questions, we make use of Demographic and Health Survey Program data from 50 low- and middle-income countries, encompassing data on 1.05 million women and their mothers spanning three decadal birth cohorts. Descriptive results demonstrate that maternal bereavement is increasingly patterned intergenerationally across cohorts, with most women experiencing the same fate as their mothers. Multivariable hazard models further show that, on average, women whose mothers were maternally bereaved have significantly increased odds of losing a child themselves. In most countries, the association is stable across cohorts; however, in select countries, the risk associated with having a bereaved mother is shrinking among more recent birth cohorts.

Ecology of the Anthropocene signals hope for consciously managing the planetary ecosystem.

Human populations have grown to such an extent that our species has become a dominant force on the planet, prompting geologists to begin applying the term Anthropocene to recognize the present moment. Many approaches seek to explain the past and future of human population growth, in the form of narratives and models. Some of the most influential models have parameters that cannot be precisely known but are estimated by expert opinion. Here we apply a unified model of ecology to provide a macroscale summary of the net effects of many microscale processes, using a minimal set of parameters that can be known. Our models match estimates of historic and prehistoric global human population numbers and provide predictions that correspond to some of the more complicated current models. In addition to fitting the data well they reveal that, amidst enormous complexity in our human and prehuman past, three key ecological discontinuities have occurred in turn: 1) becoming dominant competitors of large predators rather than their prey, 2) becoming mutualists with food species rather than acting as predators upon them, and 3) changing from a regime of uncontrolled population growth to one of controlled fertility instead. All three processes have been interlinked with cultural evolution and all three ushered in developments of the Anthropocene. Understanding the trajectories that have delivered us to this stage can help guide prudent paths into the future.

Cultural niche construction with application to fertility control: A model for education and social transmission of contraceptive use.

The evolution of a cultural trait may be affected by niche construction, or changes in the selective environment of that trait due to the inheritance of other cultural traits that make up a cultural background. This study investigates the evolution of a cultural trait, such as the acceptance of the idea of contraception, that is both vertically and horizontally transmitted within a homogeneous social network. Individuals may conform to the norm, and adopters of the trait have fewer progeny than others. In addition, adoption of this trait is affected by a vertically transmitted aspect of the cultural background, such as the preference for high or low levels of education. Our model shows that such cultural niche construction can facilitate the spread of traits with low Darwinian fitness while providing an environment that counteracts conformity to norms. In addition, niche construction can facilitate the 'demographic transition' by making reduced fertility socially accepted.

The Impact of Childhood Mortality on Fertility in Rural Tanzania: Evidence From the Ifakara and Rufiji Health and Demographic Surveillance Systems.

This manuscript examines the relationship between child mortality and subsequent fertility using longitudinal data on births and childhood deaths occurring among 15,291 Tanzanian mothers between 2000 and 2015. Generalized hazard regression analyses assess the effect of child loss on the hazard of conception, adjusting for child-level, mother-level, and contextual covariates. Results show that time to conception is most reduced if an index child dies during the subsequent birth interval, representing the combined effect of biological and volitional replacement. Deaths occurring during prior birth intervals were associated with accelerated time to conception during future intervals, consistent with hypothesized insurance effects of anticipating future child loss, but this effect is smaller than replacement effects. The analysis reveals that residence in areas of relatively high child mortality is associated with hastened parity progression, again consistent with the insurance hypothesis. Investigation of high-order interactions suggests that insurance effects tend to be greater in low-mortality communities, replacement effects tend to be stronger in high-mortality community contexts, and wealthier families tend to exhibit a weaker insurance response but a stronger replacement response to childhood mortality relative to poorer families.

Trends and factors associated with declining lifetime fertility among married women in Kenya between 2003 and 2014: an analysis of Kenya demographic health surveys.

BACKGROUND: Globally, fertility has declined in the last three decades. In sub-Saharan Africa Including Kenya, this decline started more recent and at a slower pace compared to other regions. Despite a significant fertility decline in Kenya, there are disparities in intra- and interregional fertility. Reduction in lifetime fertility has health benefits for both the mother and child, thus it is important to improve women and children health outcomes associated with high fertility. The study, therefore evaluated the factors associate with change in lifetime fertility among married women of reproductive age in Kenya between 2003 and 2014. METHODS: The study used the Kenya Demographic and Health Survey (KDHS) datasets of 2003, 2008 and 2014. Analysis of variance (ANOVA) was used to calculate the mean number of children ever born and to assess the change in fertility across different factors. Poisson regression model with robust standard errors was used to study the relationship between number of children ever born (lifetime fertility) and independent variables. A Poisson-based multivariate decomposition for the nonlinear response model was performed to identify and quantify the contribution of demographic, socioeconomic and reproductive correlates, to the change in lifetime fertility between 2003 and 2014. RESULTS: The study included 3,917, 4,002, and 7,332 weighted samples of women of reproductive age in 2003, 2008, and 2014, respectively. The mean number of children born declined from 3.8 (95% CI: 3.6-3.9) in 2003 to 3.5 (95% CI: 3.4--3.7) in 2008 and 3.4 (95% CI: 3.3-3.4) in 2014 (p = 0.001). The expected number of children reduced with the age at first sexual intercourse, the age at first marriage across the survey years, and household wealth index. Women who had lost one or more children in the past were likely to have increased number of children. The changes in the effects of women's characteristics between the surveys explained 96.4% of the decline. The main contributors to the change in lifetime fertility was the different in women level of education. CONCLUSION: The lifetime fertility declined by one-tenth between 2003 and 2014; majorly as a result of the effects of characteristics of women in terms of level of education. These highlights a need to implement education policies that promotes women education focuses on gender equality and women empowerment. Continuous strengthening of the healthcare systems (access to quality antenatal care, skilled delivery, and postpartum care) to reduce child mortality is essential.

Demographic dividend-favorable policy environment in two pre-dividend African nations: review of national policies and prospects for policy amendments in Nigeria and Tanzania.

BACKGROUND: In collaboration with local partners, we reviewed 18 national policy documents across two sub-Saharan African countries identified as pre-dividend nations by the World Bank in 2017: Nigeria and Tanzania. Our aim was to assess national policies in pre-dividend countries and to determine whether national strategies were primed to capitalize on changing demographic structures, maximally attain the demographic dividend, and augment socio-economic growth. METHODS: We conducted policy reviews by focusing on five key sectors of the Gates Institute Demographic Dividend Framework: Family Planning, Maternal and Child Health, Education, Women's Empowerment, and Labor Market. This framework was developed as a tool for countries to apply targeted policies for accelerating the demographic dividend based on their demographic structure. For each component we used a comprehensive list of indicators, defined via a systematic literature review, through which we assessed national policies aimed at maximizing the demographic dividend. RESULTS: Between the two countries, we observed persistent gaps in policies targeting family planning. Although more comprehensive, policies addressing maternal and child health, education, women's empowerment, and labor market still lagged in their specificity and measurability. We identified specific policy amendments and alternatives that Nigeria and Tanzania could consider to mitigate these gaps. We also stress the importance of designing measurable policy initiatives across sectors. CONCLUSIONS: Based on these recommendations, as Nigeria, Tanzania, and other pre-dividend nations start experiencing rapid demographic changes, they may consider implementing routine policy reviews to strengthen policies across the five key sectors and harness the benefits of a demographic dividend.

Is the mortality-fertility nexus gendered? A research note on sex differences in the impact of sibling mortality on fertility preferences.

Research guided by demographic transition theory has shown that exposure to mortality influences women's fertility preferences and behaviours. Despite the myriad contexts, methodological approaches, and linkages featured in past studies, they have shared a focus on women, leaving questions on the gendered salience of mortality exposures for adults' fertility-related outcomes unanswered. In this research note, we analyse data from three African countries with distinct fertility profiles (Nigeria, Zambia, and Zimbabwe) to examine associations between sibling mortality exposure and ideal family size among women, men, and couples. We also investigate the stability of these associations over time. The associations between adults' sibling mortality exposure and their own and their spouses' ideal family sizes vary across countries. However, the gendered nature of the results in every country and evidence of cross-spousal effects uniformly demonstrate the need to incorporate sex differences into the study of the mortality-fertility link.

Demographic and epidemiological transitions and burden of adolescent healthcare in sub-Saharan Africa: A review.

This review's main objective is to discuss how demographic and epidemiological transitions relate to the burden of adolescent healthcare in sub-Saharan Africa (SSA). The review explicitly discussed the burden of adolescent healthcare, the current African policies on adolescent healthcare, and gaps in the African policies compared with Europe and North America. We also examined how adolescent healthcare policies evolve and documented the recommended essential part of the policy for enhancing its sustainability. The burden of adolescent health is high in SSA with diseases and reproductive health-related problems prevailing among adolescents. However, variations exist in the burden of adolescent healthcare across countries in the region. While some SSA countries are currently undergoing demographic and epidemiological transition processes concerning adolescent health care, the majority are either at an early stage of the transition or yet to commence the process. Policy-makers should consider effective ways to improve adolescents' health in SSA through preventive mechanisms and a multi-dimensional approach.

The changing social gradient of marriage and cohabitation in seven Latin American countries.

While research shows that cohabitation has increased significantly among highly educated individuals in Latin America, much less is known about how the relationship between educational attainment and first union formation has changed over time and across the region's countries. Accordingly, this paper describes the changes across cohorts in the type of first union (marriage or cohabitation) entered by women from seven Latin American countries. It also analyzes trends in the relationship between women's education and the type of first union within and between these countries. Using Demographic and Health Survey (DHS) data, life tables, discrete-time event history models, and predicted probabilities were estimated to analyze the changing determinants of first-union formation. The results pointed to an overall increase in first-union cohabitation over time, with some important differences across countries. The multivariate analysis suggested that women's education influences the type and sequencing of the first union, with socioeconomically disadvantaged women increasingly likely to transition to early unions and enter cohabitation rather than marriage.

The Rise of Sonless Families in Asia and North Africa.

A neglected consequence of declining fertility is the likely rise of families with children of one sex-only sons or only daughters. Increases in such families present important demographic shifts that may weaken patrilineal family systems. We assess whether sons-only and daughters-only families rose in Asia and North Africa from the early 1990s to around 2015. Using 88 surveys and two censuses, we examine how the number and sex composition of children of mothers aged 40-49 changed across 20 countries, representing 87% of the region's population and 54% of the global population. We also compare observed trends to sex-indifferent counterfactuals, quantify contributions of fertility declines with decompositions, and investigate subnational trends in China and India. Increases in sons-only families were universal where numbers of children fell. Growth of daughters-only families was suppressed in patrilineal contexts, but these sonless families still rose significantly in 13 of 18 countries where numbers declined. By 2015, over a quarter of families in the region had only sons and nearly a fifth only daughters. There was considerable variation across countries: recent levels ranged from 28.3% to 3.4% daughters-only and from 40.1% to 6.0% sons-only. China and the rest of East Asia had the highest shares.

Life After Loss: A Prospective Analysis of Mortality Exposure and Unintended Fertility.

The relationship between mortality and fertility is a key component of demographic transition theory, placing it at the center of extensive inquiry. Among other linkages, mortality in women's communities and social networks influences their subsequent fertility. Existing demographic research assumes this is principally due to volitional mechanisms, implying that exposure to mortality consolidates women's desire to become pregnant, leading to intended fertility. Yet, insights from other disciplines suggest that mortality exposure could also increase women's unintended fertility through psychological, relational, and behavioral mechanisms. This study examines the relationships between network mortality exposure and women's hazard of pregnancy, and of unintended pregnancy specifically. We analyze two years (2009-2011) of closely spaced panel data on young Malawian women (N=1,272) enrolled in the Tsogolo la Thanzi study. Our data include information on funeral attendance and fertility desires measured weeks before conception, which is confirmed through frequent pregnancy testing. Hazard models show that the number of funerals women attend corresponds with a higher hazard of pregnancy and of unintended pregnancy specifically. These findings make clear that mortality exposure can influence fertility not by shaping women's desires but by disrupting the realization of those desires.

Growing up and moving out: Migration and the demographic transition in low- and middle-income nations.

International migration has increased since 1990, with increasing numbers of migrants originating from low- and middle-income countries (LMICs). Efforts to explain this compositional shift have focused on wage gaps and other push and pull factors but have not adequately considered the role of demographic factors. In many LMICs, child mortality has fallen without commensurate economic growth and amid high fertility. This combination increases young adult populations and is associated with greater outmigration: in the poorest countries, we estimate that a one-percentage-point increase in the five-year lagged growth rate of the population of 15-24-year-olds was associated with a 15 per cent increase in all-age outmigrants, controlling for other factors. Increases in growth of young adult populations led to 20.4 million additional outmigrants across 80 countries between 1990 and 2015. Understanding the determinants of these migration shifts should help policymakers in origin and destination countries to maximize their potential positive effects.

The changing relationship between socio-economic background and family formation in four European countries.

Family formation, a process that includes union formation, fertility, and their timing and order, has become increasingly diverse and complex in Europe. We examine how the relationship between socio-economic background and family formation has changed over time in France, Italy, Romania, and Sweden, using first wave Generations and Gender Survey data. Competing Trajectories Analysis, a procedure which combines event-history analysis with sequence analysis, allows us to examine family formation as a process, capturing differences in both the timing of the start of family formation and the pathways that young adults follow. Regarding timing, socio-economic background differences in France and Sweden have remained relatively small, whereas in Italy and Romania higher parental education has become more strongly associated with postponement. Pathways tend to diverge by socio-economic background, particularly in Sweden and France. These results indicate that while family formation patterns have changed, they continue to be stratified by socio-economic background.

Nutrition and Food Security in Bangladesh: Achievements, Challenges, and Impact of the COVID-19 Pandemic.

BACKGROUND: Bangladesh has experienced remarkable transformation in demographic, health, and nutritional status of the population. The changes have exposed the population to a number of challenges, the detrimental effect of which on health and nutrition is likely to be increased by the coronavirus disease 2019 (COVID-19) pandemic. We provide an overview of health and nutritional challenges in Bangladesh in relation to demographic transition and the COVID-19 pandemic. METHODS: We identified and reviewed recent reports, published articles, and pertinent gray literature on nutrition and food security in Bangladesh to provide historical and contextual information. RESULTS: The review identifies the progress as well as existing burden regarding nutrition and food security in Bangladesh and highlights the challenges in the coming days in regard to population growth and the COVID-19 pandemic. The country is on track to reduce all forms of childhood undernutrition, while the proportion of nutrition-related noncommunicable diseases is rising owing to changes in dietary intake, low physical activity, and sedentary lifestyle. CONCLUSIONS: Despite remarkable progress, health and nutritional status of the population in Bangladesh faces challenges, particularly in relation to demographic transition and compounded by the COVID-19 pandemic, which require concerted attention from policymakers as well as stakeholders.

Climate vulnerability of Swedish newborns: Gender differences and time trends of temperature-related neonatal mortality, 1880-1950.

BACKGROUND: In resource-poor societies, neonatal mortality (death in the first 28 days of life) is usually very high. Young infants are particularly vulnerable to environmental health risks, which are modified by socioeconomic factors that change over time. We investigated the association between ambient temperature and neonatal mortality in northern Sweden during the demographic transition. METHODS: Parish register data and temperature data in coastal Västerbotten, Sweden, between 1880 and 1950 were used. Total and sex-specific neonatal mortality was modelled as a function of mean temperature, adjusting for age, seasonality and calendar time, using discrete-time survival analysis. A linear threshold function was applied with a cut point at 14.5 °C (the minimum mortality temperature). Odds ratios (ORs) with 95% confidence intervals (CIs) were computed. Further analyses were stratified by study period (1800-1899, 1900-1929, and 1930-1950). RESULTS: Neonatal mortality was 32.1 deaths/1000 live births, higher in boys than in girls, and decreased between 1880 and 1950, with high inter-annual variability. Mean daily temperature was +2.5 °C, ranging from -40.9 °C to +28.8 °C. At -20 °C, the OR of neonatal death was 1.56 (CI 1.30-1.87) compared to the reference at +14.5 °C. Among girls, the OR of mortality at -20 °C was 1.17 (0.88-1.54), and among boys, it was 1.94 (1.53-2.45). A temperature increase from +14.5 to +20 °C was associated with a 25% increase of neonatal mortality (OR 1.25, CI 1.04-1.50). Heat- and cold-related risks were lowest between 1900 and 1929. CONCLUSIONS: In this remote sub-Arctic region undergoing socio-economic changes, we found an increased mortality risk in neonates related to low but also to high temperature. Climate vulnerability varied across time and was particularly high among boys. This demonstrates that environmental impacts on human health are complex and highly dependent on the specific local context, with many, often unknown, contributing determinants of vulnerability.