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

The current 'dramatically' high paternal ages at childbirth are not unprecedented

There is strong individual-level evidence that late fatherhood is related to a wide range of health disorders and conditions in offspring. Over the last decades, mean paternal ages at childbirth have risen drastically. This has alarmed researchers from a wide range of fields. However, existing studies have an important shortcoming in that they lack a long-term perspective. This article is a step change in providing such a long-term perspective. We unveil that in many countries the current mean paternal ages at childbirth and proportions of fathers of advanced age at childbirth are not unprecedented. Taking the detected U-shaped trend pattern into account, we discuss individual- and population-level implications of the recent increases in paternal ages at childbirth and highlight important knowledge gaps. At the individual level, some of the biological mechanisms that are responsible for the paternal age-related health risk might, at least to some degree, be counterbalanced by various social factors. Further, how these individual-level effects are linked to population health and human cognitive development might be influenced by various factors, including technical advances and regulations in prenatal diagnostics.

Economic Cycles and Entry into Parenthood: Is the Association Changing and Does it Affect Macro-Level Trends? Micro-Level Hazard and Simulation Models of Belgian Fertility Trends, 1960-2010

The association between economic cycles-typically measured in terms of GDP growth or swings in unemployment-and macro-level fertility trends has received ample attention in the literature. Compared to studies that consider macro-level fertility, individual-based models can address the association between economic cycles and specific stages of family formation (e.g. entry into parenthood) more precisely while allowing for structural factors that contribute to fertility postponement. Using population-wide longitudinal microdata from the Belgian censuses we combine discrete-time hazard models of entry into parenthood for the period 1960 to 2010 with microsimulation models to assess whether economic cycles in tandem with educational expansion can account for year-to-year variation in the proportion of women entering parenthood and variation in the pace of fertility postponement at the macro-level. Results indicate that educational expansion has been a structural driver of fertility postponement, whereas the procyclical effect of economic cycles accounts for accelerations and decelerations of fertility postponement throughout the period considered. Microsimulation of macro-level fertility trends indicates that individual-based models predict the annual proportion of women entering parenthood and the mean age at first birth with average errors of prediction below 1 per cent and 3 months, respectively, while also showing strong correlations between first differences of observed and simulated time-series. Because the extended observation window encompasses several severe recessions, we test whether the association between economic cycles and entry into parenthood has changed over time and how this affected macro-level trends, discussing several mechanisms that may account for such temporal variation.

Demography as a Field: Where We Came From and Where We Are Headed

This essay provides a series of reflections on the current state of demography as seen by four early-career researchers who are actively engaged in aspects of the discipline as varied as research, teaching, mentorship, data collection efforts, policy making, and policy advising. Despite some claims that the discipline is weakening, we showcase the great potential of the field and outline promising pathways and novel directions for the future. In so doing, we critically assess recent innovations in data quality and availability, stressing the need to "revolutionize" the way that demographic methods are taught by adopting a viewpoint that more closely reflects the rapidly changing, or "fast," nature of global social phenomena such as conflict-related displacements, environmental disasters, migration streams, pandemics, and evolving population policies. We conclude by discussing the relevance of careful demographic analyses for policy making, stressing three main points: (i) the need to make demography more visible and understandable to the public eye; (ii) the importance of engaging and co-creating with local communities to "break" the academic bubble; and (iii) the urge to counteract the spread of misinformation-a phenomenon that has become even more visible in the aftermath of the COVID-19 outbreak.

The agency of fertility plans

Fertility plans are a prominent area for agency research, and are a clear example of a misalignment between resources and agency capacity. We relied both on the idea of conversion factors of the Capability Approach and the pragmatist tradition of temporal-oriented agency to propose a framework for the study of fertility agency as the conversion process of resources into plans and behavior. We outlined said framework by using a unique dataset on fertility plans composed of open and closed questions from an Italian sample. Economic factors and imaginaries related to children and family represented the vast majority of (hindering and enabling) conversion factors. The notion of conversion factors is crucial for disentangling the network of heterogeneous elements involved in fertility agency: it allows focus to be shifted from structural factors related to social position and psychological characteristics to more situated elements that enable agency capacity.

The evolution of demographic methods

Demographic methods have been evolving ever since the birth of demography in response to changes in the field's research contents and theoretical orientations. An early core mission of finding regularities underlying macro-level population phenomena and a later interest in explaining population changes inductively facilitated the development of formal demographic techniques. A more radical methodological shift occurred after the 1960s, with the increasing availability of micro-level survey data and a shift of theoretical focus toward causal mechanisms, leading to the widespread adoption of regression-based models and methods from other social science disciplines. The future development of demographic methods will likely continue to incorporate new methods first developed in other disciplines, including techniques for analyzing unstructured "big" data, but formal demographic techniques will still play a role in population forecasting, measurements improvements, and correction of faulty data, providing foundational knowledge for other social science disciplines.

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.

Has demography witnessed a data revolution? Promises and pitfalls of a changing data ecosystem

Over the past 25 years, technological improvements that have made the collection, transmission, storage, and analysis of data significantly easier and more cost efficient have ushered in what has been described as the 'big data' era or the 'data revolution'. In the social sciences context, the data revolution has often been characterized in terms of increased volume and variety of data, and much excitement has focused on the growing opportunity to repurpose data that are the by-products of the digitalization of social life for research. However, many features of the data revolution are not new for demographers, who have long used large-scale population data and been accustomed to repurposing imperfect data not originally collected for research. Nevertheless, I argue that demography, too, has been affected by the data revolution, and the data ecosystem for demographic research has been significantly enriched. These developments have occurred across two dimensions. The first involves the augmented granularity, variety, and opportunities for linkage that have bolstered the capabilities of 'old' big population data sources, such as censuses, administrative data, and surveys. The second involves the growing interest in and use of 'new' big data sources, such as 'digital traces' generated through internet and mobile phone use, and related to this, the emergence of 'digital demography'. These developments have enabled new opportunities and offer much promise moving forward, but they also raise important ethical, technical, and conceptual challenges for the field.

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.

TiDEC: A Two-Layered Integrated Decision Cycle for Population Evolution

Agent-based simulation is a useful approach for the analysis of dynamic population evolution. In this field, the existing models mostly treat the migration behavior as a result of utility maximization, which partially ignores the endogenous mechanisms of human decision making. To simulate such a process, this article proposes a new cognitive architecture called the two-layered integrated decision cycle (TiDEC) which characterizes the individual's decision-making process. Different from the previous ones, the new hybrid architecture incorporates deep neural networks for its perception and implicit knowledge learning. The proposed model is applied in China and U.S. population evolution. To the best of our knowledge, this is the first time that the cognitive computation is used in such a field. Computational experiments using the actual census data indicate that the cognitive model, compared with the traditional utility maximization methods, cannot only reconstruct the historical demographic features but also achieve better prediction of future evolutionary dynamics.

Sibling Similarity in Education Across and Within Societies

The extent to which siblings resemble each other measures the omnibus impact of family background on life chances. We study sibling similarity in cognitive skills, school grades, and educational attainment in Finland, Germany, Norway, Sweden, the United Kingdom, and the United States. We also compare sibling similarity by parental education and occupation within these societies. The comparison of sibling correlations across and within societies allows us to characterize the omnibus impact of family background on education across social landscapes. Across countries, we find larger population-level differences in sibling similarity in educational attainment than in cognitive skills and school grades. In general, sibling similarity in education varies less across countries than sibling similarity in earnings. Compared with Scandinavian countries, the United States shows more sibling similarity in cognitive skills and educational attainment but less sibling similarity in school grades. We find that socioeconomic differences in sibling similarity vary across parental resources, countries, and measures of educational success. Sweden and the United States show greater sibling similarity in educational attainment in families with a highly educated father, and Finland and Norway show greater sibling similarity in educational attainment in families with a low-educated father. We discuss the implications of our results for theories about the impact of institutions and income inequality on educational inequality and the mechanisms that underlie such inequality.

High-to-Low (Regional) Fertility Transitions in a Peripheral European Country: The Contribution of Exploratory Time Series Analysis

Diachronic variations in demographic rates have frequently reflected social transformations and a (more or less evident) impact of sequential economic downturns. By assessing changes over time in Total Fertility Rate (TFR) at the regional scale in Italy, our study investigates the long-term transition (1952–2019) characteristic of Mediterranean fertility, showing a continuous decline of births since the late 1970s and marked disparities between high- and low-fertility regions along the latitude gradient. Together with a rapid decline in the country TFR, the spatiotemporal evolution of regional fertility in Italy—illustrated through an exploratory time series statistical approach—outlines the marked divide between (wealthier) Northern regions and (economically disadvantaged) Southern regions. Non-linear fertility trends and increasing spatial heterogeneity in more recent times indicate the role of individual behaviors leveraging a generalized decline in marriage and childbearing propensity. Assuming differential responses of regional fertility to changing socioeconomic contexts, these trends are more evident in Southern Italy than in Northern Italy. Reasons at the base of such fertility patterns were extensively discussed focusing—among others—on the distinctive contribution of internal and international migrations to regional fertility rates. Based on these findings, Southern Italy, an economically disadvantaged, peripheral region in Mediterranean Europe, is taken as a paradigmatic case of demographic shrinkage—whose causes and consequences can be generalized to wider contexts in (and outside) Europe.

Children of the (gender) revolution: A theoretical and empirical synthesis of how gendered division of labour influences fertility

Gender equity theories of fertility broadly predict that the lowest fertility in high-income settings will be seen in women facing a 'dual burden' of both paid and unpaid labour responsibilities, but that fertility will increase when male partners share domestic labour. Here we provide a critique of some gender equity theories of fertility in demography, and restate the hypothesis in terms of complementarity between partners. Further, we suggest authors use an interdisciplinary approach, such as integrating perspectives from evolutionary theory and the 'Traits-Desires-Intentions-Behaviour' framework, to provide some consistency to this diverse literature. Building on this theoretical synthesis, we perform a systematic review of 95 pieces of analysis. This broadly supports the idea that fertility will be low where women face a dual burden, which is particularly evident among macro-level studies, micro-level analyses investigating progression to subsequent children, and studies which do not use gender role attitudes as an independent variable.

Linking social class inequalities, labor market status, and fertility: An empirical investigation of second births

I outline a theoretical background for interpreting the effects of social class on fertility, based on social class and welfare regime theory. Social class differentials lead to different levels of economic wellbeing and security, compatibility of employment and childcare roles, and of gender equality. I hypothesize that class-specific combinations of these variables result in different incentives for and constraints on family formation, and thus different fertility levels. I use the Spanish sample of the European Union Statistics on Income and Living Conditions for the years 2004-2015 and event history analysis techniques to analyze second-birth probabilities. A substantial positive effect of social class on second birth probabilities was found. The results also indicated that the mechanisms concerning the effects of class do not work in a monotonic way, and that specific combinations of mechanisms are relevant for each social group. Overall, the analyses showed that social class is not only key to understand intracountry differentials in fertility but also useful to understand the functioning of the welfare regime and its relationship to overall levels of fertility.

Global and local correlations of Hajnal's household formation markers in historical Europe: A cautionary tale

Previous scholarship has assumed global correlations between premarital service in husbandry, marriage age, the extent to which marriage coincided with the attainment of household headship, and the nuclear household structure. According to John Hajnal, these were the four core principles of historical household formation systems. However, whether such correlations applied universally across Europe remains uncertain. We test this possibility by applying both global and local (geographically weighted) measures of correlation to data for 256 rural populations from historical Europe. We demonstrate that local correlations diverge considerably from the global results. The mutual associations between household formation markers exhibit considerable spatial drifts and important spatial gradients, and the numbers of joint combinations of these associations far exceed those predicted by Hajnal. We argue that the global relationship patterns that Hajnal promoted may lead to incorrect interpretations of historical family systems, and may detract from our understanding of their actual mechanics.

Contribution of the Rise in Cohabiting Parenthood to Family Instability: Cohort Change in Italy, Great Britain, and Scandinavia

In this study, we investigate through microsimulation the link between cohabiting parenthood and family instability. We identify mechanisms through which increases in cohabiting parenthood may contribute to overall increases in separation among parents, linking micro-level processes to macro-level outcomes. Analyses are based on representative surveys in Italy, Great Britain, and Scandinavia (represented by Norway and Sweden), with full histories of women’s unions and births. We first generate parameters for the risk of first and higher-order birth and union events by woman’s birth cohort and country. The estimated parameters are used to generate country- and cohort-specific populations of women with stochastically predicted family life courses. We use the hypothetical populations to decompose changes in the percentage of mothers who separate/divorce across maternal birth cohorts (1940s to 1950s, 1950s to 1960s, 1960s to 1970s), identifying how much of the change can be attributed to shifts in union status at first birth and how much is due to change in separation rates for each union type. We find that when cohabiting births were uncommon, increases in parents’ separation were driven primarily by increases in divorce among married parents. When cohabiting parenthood became more visible, it also became a larger component, but continued increases in parents’ divorce also contributed to increasing parental separation. When cohabiting births became quite common, the higher separation rates of cohabiting parents began to play a greater role than married parents’ divorce. When most couples had their first birth in cohabitation, those having children in marriage were increasingly selected from the most stable relationships, and their decreasing divorce rates offset the fact that increasing proportions of children were born in somewhat less stable cohabiting unions.

Stress and adolescent well-being: the need for an interdisciplinary framework

Stress and strain among adolescents have been investigated and discussed largely within three separate disciplines: mental health, where the focus has been on the negative effects of stress on emotional health; criminology, where the emphasis has been on the effects of strain on delinquency; and biology, where the focus has been to understand the effects of stress on physiology. Recently, scholars have called for increased multilevel developmental analyses of the bio-psychosocial nature of risk and protection for behaviors of individuals. This paper draws on several different but converging theoretical perspectives in an attempt to provide an overview of research relevant to stress in adolescence and puts forth a new framework that aims to provide both a common language and consilience by which future research can analyze the effects of multiple biological, social and environmental factors experienced during specific developmental periods, and cumulatively over time, on harmful behavior during adolescence. We present a framework to examine the effects of stress on diverse behavioral outcomes among adolescents, including substance use, suicidal behavior, self-inflicted harm, and delinquency.

Rethinking mortality deceleration

The evolution of mortality shows a marked deceleration at older ages. This phenomenon is generally thought to be an effect of selection: mortality decelerates because it progressively selects the most robust individuals in the cohort. Other processes, however, may contribute to mortality deceleration as well. People may not be passive in the face of ageing and may try to counter it by modifying their behaviours and lifestyles. In this paper, I propose a method to test whether selection is to be considered the unique mechanism responsible for mortality deceleration. I applied this method to the life tables of selected female cohorts drawn from the Human Mortality Database. The results indicate mortality decelerates more rapidly than predicted by the selection theory.

Societal Agreement on Gender Role Attitudes and Childlessness in 38 Countries

Many authors argue that levels of childlessness and fertility are a function of changing gender relations, but the mechanisms behind this association remain unclear and mainly untested. This study argues that the societal variation in gender role attitudes explains the link: a great variation in attitudes among potential partners leads to uncertainty and conflicts, which depresses people's propensity for parenthood. This idea is tested with multilevel logistic regression models for 6305 individuals in 38 countries on all continents, using ISSP 2012 data. Measures for the average gender role attitude in the society as well as the dispersion in attitudes are regressed on whether individuals have at least one child or are childless. Attitudes are captured using factor analysis and are opinions towards the gendered division of given tasks and privileges, such as childrearing or the uptake of parental leave. The dispersion in attitudes is the standard deviation of the factor variable in the given country. The analysis gives support to the hypothesis: the greater the variation in gender role attitudes, the higher the chance for individuals to remain childless. The association is significant and holds against various robustness checks.

Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors

A large body of literature has demonstrated a positive relationship between education and age at first birth. However, this relationship may be partly spurious because of family background factors that cannot be controlled for in most research designs. We investigate the extent to which education is causally related to later age at first birth in a large sample of female twins from the United Kingdom (N = 2,752). We present novel estimates using within-identical twin and biometric models. Our findings show that one year of additional schooling is associated with about one-half year later age at first birth in ordinary least squares (OLS) models. This estimate reduced to only a 1.5-month later age at first birth for the within-identical twin model controlling for all shared family background factors (genetic and family environmental). Biometric analyses reveal that it is mainly influences of the family environment-not genetic factors-that cause spurious associations between education and age at first birth. Last, using data from the Office for National Statistics, we demonstrate that only 1.9 months of the 2.74 years of fertility postponement for birth cohorts 1944-1967 could be attributed to educational expansion based on these estimates. We conclude that the rise in educational attainment alone cannot explain differences in fertility timing between cohorts.

Choosing the choice: Reflections on modelling decisions and behaviour in demographic agent-based models

This paper investigates the issues associated with choosing appropriate models of choice for demographic agent-based models. In particular, we discuss the importance of context, time preference, and dealing with uncertainty in decision modelling, as well as the heterogeneity between agents in their decision-making strategies. The paper concludes by advocating empirically driven, modular, and multi-model approaches to designing simulations of human decision-making, given the lack of an agreed strategy for dealing with any of these issues. Furthermore, we suggest that an iterative process of data collection and simulation experiments, with the latter informing future empirical data collection, should form the basis of such an endeavour. The discussion is illustrated with reference to selected demographic agent-based models, with a focus on migration.

Considering climate in studies of fertility and reproductive health in poor countries

Understanding the links between climate and fertility and reproductive health outcomes in poor countries is a major ethical and policy imperative. However, doing so will require researchers in population sciences and in earth and climate sciences to merge their expertise. To this end, the dominant theoretical frameworks and readily available geospatial population data used by social scientists provide a starting point for climate and physical scientists to think about the mechanisms that link climate and weather to fertility and reproductive health, and available climate data and analytic strategies can be used to develop research that considers different scales of influence.