The ABC of demographic behaviour: how the interplays of alleles, brains, and contexts over the life course should shape research aimed at understanding population processes

Population Studies at 75 years: An empirical review

Population Studies advances research on fertility, mortality, family, migration, methods, policy, and beyond, yet it lacks a recent, rigorous review. We examine all papers published between 1947 and 2020 (N = 1,901) and their authors, using natural language processing, social network analysis, and mixed methods that combine unsupervised machine learning with qualitative coding. After providing a brief history, we map the evolution in authorship and papers towards shorter, multi-authored papers, also finding that females comprise 33.5 per cent of authorship across the period under study, with varied sex ratios across topics. Most papers examine fertility, mortality, and family, studying groups and change, but topics vary over time. Children are rarely studied, and research on women focuses on family planning, fertility decline, and unions, whereas key domains for research on men are migration, historical demography (war, famine), and employment. Research on Africa and Asia focuses on family planning, with work on fertility decline concentrated on North America and Europe, consistent with theories of demographic transition. Our resulting discussion identifies future directions for demographic research.

Demography and the rise, apparent fall, and resurgence of eugenics

Demography was heavily involved in the eugenics movement of the early twentieth century but, along with most other social science disciplines, largely rejected eugenic thinking in the decades after the Second World War. Eugenic ideology never entirely deserted academia, however, and in the twenty-first century, it is re-emerging into mainstream academic discussion. This paper aims, first, to provide a reminder of demography's early links with eugenics and, second, to raise awareness of this academic resurgence of eugenic ideology. The final aim of the paper is to recommend ways to counter this resurgence: these include more active discussion of demography's eugenic past, especially when training students; greater emphasis on critical approaches in demography; and greater engagement of demographers (and other social scientists) with biologists and geneticists, in order to ensure that research which combines the biological and social sciences is rigorous.

Theory and explanation in demography: The case of low fertility in Europe

In the 50th anniversary edition of Population Studies, John Hobcraft commented that demographers spend too little time trying to explain the phenomena they measure and describe. A quarter of a century on, this paper looks at the state of theory and explanation in contemporary demography. I ask how demographers have approached the task of explanation since Hobcraft's comment, grounding the discussion in the mainstream literature on low fertility in Europe. Using selected examples, I critically review macro- and micro-level approaches to explanation, highlighting some of the philosophical problems that each encounters. I argue that different conceptions of what demography is, and the explanatory language fertility researchers use, lead to differences in explanatory strategies that are rarely explicitly recognized. I also consider how critical theories challenge demographers to think in new ways. Despite the increasing attention paid to theory and explanation, I conclude that more engagement with the philosophy of social sciences is needed before fertility researchers can legitimately claim their studies do as much to explain and understand as to quantify and describe.

Life satisfaction favors reproduction. The universal positive effect of life satisfaction on childbearing in contemporary low fertility countries

Do people with higher life satisfaction have more children? Having children requires considerable energy and investment on the part of parents. However, even in countries where contraceptives are easily available and widely used, where having children is optional and most of time the result of an intended action, parenthood has not gone "out of fashion". This paper tests the hypothesis that higher life satisfaction fosters reproductive behavior. We argue that people satisfied with their overall life feel better prepared to start the monumental task of childrearing. If, it is suggested, life satisfaction facilitates fertility, then this positive link should be observable in contemporary low fertility societies. The hypothesis is tested by taking overall life satisfaction as a determinant of fertility behavior using long longitudinal data available for developed countries: namely for Australia, Germany, Russia, South Korea, Switzerland, the United Kingdom, and the United States. We find that higher levels of subjective well-being are, indeed, associated with a higher probability of having children in all the countries considered. We, therefore, conclude that life satisfaction favors reproduction, at least in low fertility societies.

Emotional Variation and Fertility Behavior

Emotional influences on fertility behaviors are an understudied topic that may offer a clear explanation of why many couples choose to have children even when childbearing is not economically rational. With setting-specific measures of the husband-wife emotional bond appropriate for large-scale population research matched with data from a long-term panel study, we have the empirical tools to provide a test of the influence of emotional factors on contraceptive use to limit fertility. This article presents those tests. We use long-term, multilevel community and family panel data to demonstrate that the variance in levels of husband-wife emotional bond is significantly associated with their subsequent use of contraception to avert births. We discuss the wide-ranging implications of this intriguing new result.

Integrating macro- and micro-level approaches in the explanation of population change

Demographers study population change across time and place, and traditionally they place a strong emphasis on a long-range view of population change. This paper builds on current reflections on how to structure the study of population change and proposes a two-stage perspective. The first stage, discovery, focuses on the production of novel evidence at the population level. The second stage, explanation, develops accounts of demographic change and tests how the action and interaction of individuals generate what is discovered in the first stage. This explanatory stage also provides the foundation for the prediction of demographic change. The transformation of micro-level actions and interactions into macro-level population outcomes is identified as a key challenge for the second stage. Specific instances of research are discussed.

Evolutionary contributions to the study of human fertility

Demography, lacking an overarching theoretical framework of its own, has drawn on theories in many other social sciences to inform its analyses. The aim of this paper is to bring to the demographic community's attention research in the evolutionary sciences on fertility, and to demonstrate that evolutionary theory can be another useful tool in the demographer's toolkit. I first dispel some myths which impede the incorporation of evolutionary theory into demography: I make it clear that evolutionary explanations do not assume that all human behaviour is hardwired and functions to maximize genetic fitness; that they are able to explain variation in human behaviour; and that they are not necessarily alternatives to social science explanations. I then describe the diversity of work on fertility by evolutionary researchers, particularly human evolutionary ecologists and cultural evolutionists, and illustrate the usefulness of the evolutionary approach with examples of its application to age at first birth and the fertility transition.

Who Delays Childbearing? The Associations Between Time to First Birth, Personality Traits and Education

Using data from a large-scale survey, the British Household Panel Survey, this paper assesses the influence of personality traits on the timing of first childbirth and investigates whether, and in what way, personality traits explain the differences in maternity timing across educational groups. We estimate a log-logistic model of the time to first childbirth and show that there is a statistically significant relationship between the Big Five personality traits and the timing of motherhood. The results also show that highly qualified women who are 'open-minded' have the lowest hazards of childbirth, lower than similar less educated counterparts.

Genetic influence on age at first birth of female twins born in the UK, 1919-68

Using a sample of monozygotic (945, 42 per cent) and dizygotic (1,329, 58 per cent) twin pairs born 1919-68 in the UK, we applied innovative tobit models to investigate genetic and environmental influences on age at first birth (AFB). We found that a substantial part (40 per cent) of the variation in AFB is caused by latent family characteristics. Genetic dispositions (26 per cent) play a more important role than the shared environment of siblings (14 per cent), with the non-shared environment/measurement error having the strongest influence (60 per cent). Like previous studies, this study reveals marked changes in estimates over time, and supports the idea that environmental constraints (war or economic crisis) suppress and normative freedom (sexual revolution) promotes the activation of genetic predispositions that affect fertility. We show that the exclusion of censored information (i.e., on the childless) by previous studies biased their results.

Population ageing in a lifecourse perspective: developing a conceptual framework

Population ageing is a global trend that affects individual life plans, family arrangements, market structures, care provisions and pension schemes. We combine insights from demography and lifecourse research to understand better the causes of population ageing. Demography explains population ageing by describing changes in fertility, mortality and migration rates. Lifecourse research argues that these rates are interconnected because they are embedded in the lifecourses of individuals. An individual's experiences at an early age can influence behaviours at a later age, thereby creating continuity throughout the lifecourse. Additionally, lifecourse research underlines that social networks – such as families – and countries influence lifecourse. Thus, historical events and past experiences have already set the course for today's demographic changes. Moreover, the effects of policies that strive to influence population ageing will not be evident for years or even decades to come. This paper introduces a conceptual framework that explains how the lifecourse perspective can be applied to the phenomenon of population ageing and illustrates the framework through a case study of Germany. The case study highlights that insights from the micro-, meso- and macro-levels need to be combined to achieve a deeper understanding of population ageing. Scholars can use the framework presented in this paper as a guideline for merging arguments from demography and lifecourse research in future studies.

Happiness: before and after the kids

Understanding how having children influences parents' subjective well-being ("happiness") has great potential to explain fertility behavior. We study parental happiness trajectories before and after the birth of a child, using large British and German longitudinal data sets. We account for unobserved parental characteristics using fixed-effects models and study how sociodemographic factors modify the parental happiness trajectories. Consistent with existing work, we find that happiness increases in the years around the birth of a first child and then decreases to before-child levels. Moreover, happiness increases before birth, suggesting that the trajectories may capture not only the effect of the birth but also the broader process of childbearing, which may include partnership formation and quality. Sociodemographic factors strongly modify this pattern. Those who have children at older ages or who have more education have a particularly positive happiness response to a first birth; and although having the first two children increases happiness, having a third child does not. The results, which are similar in Britain and Germany, suggest that having up to two children increases happiness, and mostly for those who have postponed childbearing. This pattern is consistent with the fertility behavior that emerged during the second demographic transition and provides new insights into low and late fertility.

FERTILITY INTENTIONS AND EARLY LIFE HEALTH STRESS AMONG WOMEN IN EIGHT INDIAN CITIES: TESTING THE REPRODUCTIVE ACCELERATION HYPOTHESIS

In life history theory, early life adversity is associated with an accelerated reproductive tempo. In harsh and unpredictable conditions in developing societies fertility is generally higher and the reproductive tempo faster than in more secure environments. This paper examines whether differences in female anthropometry, particularly adult height, are associated with fertility intentions of women in urban environments in India. The study population consists of women aged 15–29 (N=4485) in slums and non-slums of eight Indian cities in the National Family Health Survey (NFHS) of 2005–2006. Adult height is taken as a proxy for early childhood health and nutritional condition. Fertility intentions are examined by using two variables: the desire to have a child or another child, and to have it relatively soon, as indicative of accelerated reproductive scheduling. Evidence supporting the acceleration hypothesis is found in two urban frames out of 26 examined in a two-staged multinomial logistic model. In three cases, the relationship between fertility intentions and height is the opposite than expected by the acceleration hypothesis: taller women have a higher predictive probability of desiring a(nother) child and/or narrower birth spacing. Potential explanations for the partly contradictory relationship between the childhood health indicator and fertility intentions are discussed.

Polygynous contexts, family structure, and infant mortality in sub-saharan Africa

Contextual characteristics influence infant mortality above and beyond family-level factors. The widespread practice of polygyny is one feature of many sub-Saharan African contexts that may be relevant to understanding patterns of infant mortality. Building on evidence that the prevalence of polygyny reflects broader economic, social, and cultural features and that it has implications for how families engage in the practice, we investigate whether and how the prevalence of polygyny (1) spills over to elevate infant mortality for all families, and (2) conditions the survival disadvantage for children living in polygynous families (i.e., compared with monogamous families). We use data from Demographic and Health Surveys to estimate multilevel hazard models that identify associations between infant mortality and region-level prevalence of polygyny for 236,336 children in 260 subnational regions across 29 sub-Saharan African countries. We find little evidence that the prevalence of polygyny influences mortality for infants in nonpolygynous households net of region-level socioeconomic factors and gender inequality. However, the prevalence of polygyny significantly amplifies the survival disadvantage for infants in polygynous families. Our findings demonstrate that considering the broader marital context reveals important insights into the relationship between family structure and child well-being.

A model comparison approach shows stronger support for economic models of fertility decline

The demographic transition is an ongoing global phenomenon in which high fertility and mortality rates are replaced by low fertility and mortality. Despite intense interest in the causes of the transition, especially with respect to decreasing fertility rates, the underlying mechanisms motivating it are still subject to much debate. The literature is crowded with competing theories, including causal models that emphasize (i) mortality and extrinsic risk, (ii) the economic costs and benefits of investing in self and children, and (iii) the cultural transmission of low-fertility social norms. Distinguishing between models, however, requires more comprehensive, better-controlled studies than have been published to date. We use detailed demographic data from recent fieldwork to determine which models produce the most robust explanation of the rapid, recent demographic transition in rural Bangladesh. To rigorously compare models, we use an evidence-based statistical approach using model selection techniques derived from likelihood theory. This approach allows us to quantify the relative evidence the data give to alternative models, even when model predictions are not mutually exclusive. Results indicate that fertility, measured as either total fertility or surviving children, is best explained by models emphasizing economic factors and related motivations for parental investment. Our results also suggest important synergies between models, implicating multiple causal pathways in the rapidity and degree of recent demographic transitions.

Clustering of deaths in families: infant and child mortality in historical perspective

This introduction surveys the field of family clustering of deaths and discusses the contributions in this special issue. The main focus is on mortality in historical contexts. Clustering of deaths in families has been found both in historical and contemporary populations, and we argue that the 'family approach' to infant and child mortality yields important and interesting insights for our understanding of different mortality patterns and the mortality transition. The articles in this issue, representing different but complementary approaches to the problem of death clustering, demonstrate that we should be aware of the strong family effects on child health, but also that we need to develop adequate methods for the analysis of this complex phenomenon. Here we discuss several explanations for death clustering, such as different biodemographic factors and those focusing on socioeconomic and cultural variables. We also discuss some of the methodological challenges in studying family clustering, and emphasize the need for comparison and the adoption of common measures.

A global perspective on happiness and fertility

The literature on fertility and happiness has neglected comparative analysis. We investigate the fertility/happiness association using data from the world values surveys for 86 countries. We find that, globally, happiness decreases with the number of children. This association, however, is strongly modified by individual and contextual factors. Most importantly, we find that the association between happiness and fertility evolves from negative to neutral to positive above age 40, and is strongest among those who are likely to benefit most from upward intergenerational transfers. In addition, analyses by welfare regime show that the negative fertility/ happiness association for younger adults is weakest in countries with high public support for families, and the positive association above age 40 is strongest in countries where old-age support depends mostly on the family. Overall these results suggest that children are a long-term investment in well-being, and highlight the importance of the life-cycle stage and contextual factors in explaining the happiness/fertility association.

Reflections on the incorporation of biomeasures into longitudinal social surveys: an international perspective

This article is concerned with the underlying rationales for including biomeasures in longitudinal social surveys. In particular, it seeks to draw out the potential advantages of incorporating biomeasures in household panel studies for advancing our understanding of behaviors. A key emphasis is on elaborating pathways from biology through the brain/mind to behaviors and outcomes, particularly for social, demographic, economic, and health domains. The article elaborates these themes and illustrates them within the context of international experience. It lays out some of the key issues concerning conceptualization and operationalization of the integration of biomeasures into surveys. The next section considers the particular issues concerned with these opportunities and innovations for household panel studies. This is followed by a brief summary of the extent to which biomeasures have been incorporated into longitudinal social surveys, especially outside the United States. The final main section considers a wide range of strategic issues in the the collection of biomeasures in household panel studies and is followed by a brief conclusion.

Biodemography Comes of Age

Biodemography has emerged and grown over the last fifteen years, with loyal and farsighted support from its patrons. As it enters what might be called its adolescence as a field, it faces challenges along with abounding opportunities. One challenge is to continue to generate knowledge that contributes to human health and well-being. A second is to insist on high standards of quality control within its crossdisciplinary environment. Opportunities appear in a variety of directions, including mathematical modeling, genomic analyses, and field studies of aging in the wild.

The effects of siblings on the migration of women in two rural areas of Belgium and the Netherlands, 1829-1940

This study explores the extent to which the presence and activities of siblings shaped the chances of women migrating to rural and urban areas in two rural areas of Belgium and the Netherlands during the second half of the nineteenth and first decades of the twentieth century. Shared-frailty Cox proportional hazard analyses of longitudinal data from historical population registers show that siblings exerted an additive impact on women's migration, independently of temporal and household characteristics. Just how siblings influenced women's migration depended on regional modes of production and on employment opportunities. In the Zeeland region, sisters channelled each other into service positions. In the Pays de Herve, where men and women found industrial work in the Walloon cities, women were as much influenced by their brothers' activities. Evidence is found for two mechanisms explaining the effects of siblings: micro-economic notions of joint-household decision-making and social capital theory.