The life course boat: A theoretical framework for analyzing variation in family lives across time, place, and social location

Objective: We propose a life course theoretical framework for understanding variation in family life courses between birth cohorts (historical time), societies (place), and social groups (social location). Building on the life course paradigm, we explain how key predictors on different levels of analysis can reinforce, precondition, counteract, preclude, or alter each other ’ s influence on family life courses in specific contexts. The proposed framework re-organizes and extends core principles of the life course paradigm into family life course predictors and outcomes on the individual, relational, and population levels. Background: The life course approach is a well-recognized interdisciplinary paradigm in family research but often remains too abstract to guide hypotheses about family life course variation. Method: We demonstrate the utility of the proposed framework with a qualitative case study on family life courses in Senegal and a quantitative case study on family life course change between Baby Boomer and Millennial cohorts in the United States using sequence analysis. Results: Findings of the two example applications support that fertility decline in Senegal was primarily driven by material considerations and not by ideational change and that family life course de-standardization was greater


INTRODUCTION
Families vary widely across historical time, regions of the world, and social groups defined by gender, race, class, and religion, among others.Most research on historical change and global variation in family lives separates specific family events or domains, such as partnering, fertility, or household structures (e.g., Pesando, 2018;Ruggles, 2010;Therborn, 2014).This literature informs about the global patterns of divergence and convergence in various family indicators and the drivers of family change.A largely separate literature uses a longitudinal life course perspective that considers how the occurrence, timing, and sequencing of family states in individual lives are interrelated and how contextual factors jointly shape them.Life course theory (Bernardi et al., 2019;Elder, 1998;Elder et al., 2003;Mayer, 2009) provides an important starting point for understanding differences in the occurrence, timing, and sequencing of family events in individuals' lives in different contexts.
The need to approach families from a life course perspective is undisputed and shared across core disciplines concerned with family research, including anthropology, demography, psychology, and sociology (Bengtson & Allen, 1993;Elder et al., 2003).The life course paradigm is firmly rooted in psychological perspectives on human development and aging (Baltes, 1987;Elder, 1975) and comparative stratification research (Fasang & Mayer, 2023).Family lives only took center stage in the life course tradition from the 1990s onward, with a growing interest in gender inequalities and the gendered interplay between work and family lives (Aisenbrey & Fasang, 2017;Allmendinger et al., 1993;Kohli, 2007;Krüger & Levy, 2001).However, the life course as a general interdisciplinary paradigm comes with several limitations for family research that we seek to address in the proposed framework.
First, rather than reducing complexity, recent elaborations of life course theory move towards a more nuanced display of complexity, as exemplified by the "life course cube" (Bernardi et al., 2019).The "life course cube" masterfully alerts to the complexities of multiple interrelated dimensions of the life course (time, levels, domains) but convolutes life course features as outcomes and predictors and is difficult to channel into testable hypotheses in specific fields, such as family life courses.Our framework seeks to reduce complexity to aid hypothesis development by clearly separating family life course outcomes from potentially interacting predictors on different levels of analysis.
Second, searching for widely generalizable findings curtailed the innovative potential of the life course paradigm to identify key interrelated predictors of family life course variation in their unique historical time, place, and social location.The general life course paradigm offers little guidance on the relative importance of different predictors of life course variation.Unlike psychological accounts of aging, the strength of the sociological life course perspective arguably is to highlight how individual life courses are not generalizable but highly specific to given sociohistorical locations.Mayer's (2004) call for a "differential life course sociology" and the notion of vital "conjunctures" that signify specific combinations of contextual conditions in a given situation (Johnson-Hanks et al., 2011) emphasize the importance of context in shaping family lives.We conceptualize "contexts" that shape family life courses as sets of micro-, meso-, and macro-level predictors.Our framework highlights that family life course predictors not only have direct effects that operate in the same way but also can interact with each other.As a result, the joint presence or absence of multiple key predictors matters for the observed family life course outcomes.For instance, the presence of one predictor, such as strong social control in family networks, can reinforce the influence of another predictor, such as the presence of religious high fertility norms.Below, we elaborate on likely interacting relationships between predictors that shape family life courses (reinforcing, off-setting, counteracting, precluding, and altering).Uncovering the joint imprint of contextual conditions on family lives calls for incorporating the global variety of contextual conditions.To date, however, life course research remains heavily focused on a small set of affluent capitalist democracies in the global Northwhich constitute <15% of the global population (Trask, 2018; for recent exceptions, see Buyukkececi et al., 2023;Madero-Cabib & Cabello-Hutt, 2022;Van Winkle & Wen, 2023).
Third, the general life course paradigm initially focused more on life course comparisons across cohorts and regions with lesser emphasis on life course variation by social locations, such as gender, race, and social class.Our framework gives the social stratification of family life courses equal weight.Contexts as sets of interacting predictors can vary just as much, or even more, between social classes or racial groups as between cohorts or regions.Social location can define individuals' life chances and the opportunity structure through which they navigate their family lives, as much as being born in a given country or year.
We propose a theoretical framework that adapts the core principles of the life course paradigm to guide hypotheses on family life course variation across time, place, and social location.Our framework aims for complexity reduction, highlights specificity rather than generalizability, and calls for incorporating the global variation of contextual conditions and social locations that shape family life courses.To this end, we (1) explicate key interacting relationships between predictors of family life courses and (2) systematize family life course outcomes on the individual, relational, and population levels.We illustrate the proposed framework with a qualitative and a quantitative case study.

THE LIFE COURSE PARADIGM AND ITS LIMITATIONS FOR FAMILY RESEARCH
The life course paradigm has become an influential driver of family scholarship (Konietzka & Kreyenfeld, 2021).Building on foundational ideas on generations (Mannheim, 1952), cohorts (Ryder, 1965), and age norms (Neugarten et al., 1965), Elder (1975) promoted the life course paradigm as an interdisciplinary framework for guiding research on human lives.For introductions to life course sociology see Elder et al. (2003) and Mayer (2009).For an overview of life course approaches in family sociology and demography see Fasang and Mayer (2020) and Konietzka and Kreyenfeld (2021).Elder et al. (2003) outline five core principles of the life course paradigm, which remain widely cited by family scholars: 1. Life-Span Development: Human development and aging are lifelong processes.2. Agency: Individuals construct their life course through their choices and actions within the opportunities and constraints of history and social circumstances.3. Time and Place: Individuals' lives are embedded in and shaped by the historical times and places they live in.4. Timing: The developmental antecedents and consequences of life transitions, events, and behavioral patterns vary according to their timing in a person's life.
5. Linked Lives: Lives are lived interdependently, and sociohistorical influences are expressed through this network of shared relationships.
These principles apply to human lives regardless of historical and sociocultural context, which is one reason for their broad appeal.However, they have several limitations regarding our objective of explaining variation in family life courses across time, place, and social location.
First, the core principles convolute features of the life course as an outcome and predictors that shape life courses.Specifically, the principles of lifelong development (1) and timing (4) refer to integral parts of the life course itself, suggesting that the life course should be interpreted as a longitudinal sequence of interconnected stages.They imply that we should look at family life courses holistically rather than at a single, decontextualized event or aggregate patterns of transitions and account for path dependency of later life events based on earlier life events.The principles of agency (2), time and place (3), and linked lives (5) relate to determinants of variation in life courses on the micro, macro, and meso levels.However, it is not specified how these three principles, that is, predictors on different levels of analysis, interact to produce qualitatively different life courses.
Second, the core principles of the life course paradigm remain vague on what constitutes a life course outcome and implicitly suggest a strong focus on individual-level life course outcomes.Specifically, the principles of lifelong development (1), agency (2), and timing (4) suggest targeting hypotheses on individual development over time.The principle of linked lives implies a relational perspective suggesting a focus on outcomes conceptualized on the level of dyads or smaller social networks.However, in family research and demography, aggregate patterns of family life courses on the population level have been a central theoretical interest (e.g., Billari, 2001;Elzinga & Liefbroer, 2007;Pesando et al., 2021;Van Winkle & Fasang, 2021).For example, theories on the second demographic transition (Lesthaeghe & van de Kaa, 1986) and increasing life course destandardization and individualization (Brückner & Mayer, 2005), or diverging destinies (McLanahan, 2004) make predictions about aggregate patterns of family life courses on the population level.Specifying theoretically relevant concepts of family life courses as outcomes on different levels of analysis is thus necessary to guide hypotheses anchored in established family and life course theories.
Third and relatedly, the core principles do not account for the multidimensionality of life courses and the continual mutual influence of events in different life domains, which suggest treating them as joint outcome concepts (Aisenbrey & Fasang, 2017;Fasang & Aisenbrey, 2022;Mayer, 2004).Numerous studies highlight the interplay of work and family lives and to a lesser extent, between family lives, migration, and health trajectories.Life course norms create linkages between life domains by specifying which life events in one domain should be fulfilled before transitions in the other are deemed acceptable and appropriate (Beaujouan & Berghammer, 2019).For example, many societies consider completing education, moving out of the parental home, and attaining an economically secure job as preconditions for marriage and parenthood (Cherlin, 2020;Naafs, 2013).
Despite the limitations of the general life course paradigm for studying family lives, there are strong reasons why we need a life course perspective to address critical questions in family research.Classic theories on family change, including modernization theory (Lipset & Bendix, 1959), the second demographic transition (Lesthaeghe & van de Kaa, 1986), and diverging destinies (McLanahan, 2004) strongly focus on aggregate processes of family change.The life course perspective offers a dynamic micro-level foundation of aggregate family change through (1) conceptualizing how family events and states are connected through their joint occurrence, timing, and sequencing in individual life courses that aggregate to population-level patterns of family change and (2) highlighting family change through cohort replacement.Focusing on social change through cohort replacement re-directs attention to the specific conditions through which different birth cohorts pass as they age, quickly rendering grand narratives about aggregate linear trends implausible.Therefore, a theoretical framework to explain variation in family life courses should also guide predictions about nonlinear and fluctuating changes in family life courses across birth cohorts that can diverge in different regions of the world and between social groups.
As a recent adaptation of life course theory, Bernardi et al. (2019) proposed a "life course cube" based on three core dimensions: time, levels (intraindividual, individual, and supraindividual), and domains (e.g., work and family).These dimensions are connected through first-order interdependencies (past-present-future, multilevel, and interdomain) and secondorder interdependencies among each other.The life course cube resonates with our criticism of Elder et al.'s principles in highlighting inter-domain dependencies, for example, between work and family lives.However, the life course cube also lumps integral parts of individual life courses as outcomes and their determinants into a single conceptual construct that does not naturally guide the specification of concrete testable hypotheses on variation in family life courses (see Mayer, 2019 for a more detailed critique).
More generally, the general life course paradigm and the life course cube claim a much broader scope as a theoretical underpinning for interdisciplinary life course research (see Kreyenfeld & Konietzka, 2021) compared with our narrower goal of a life course framework for analyzing variation in family lives.The ambition to provide theoretical foundations of such a broad scope restricts their applicability to empirical family life course research.Instead, we advocate for life course theories of the middle range that channel general life course principles into testable and relevant hypotheses on family life course variation across time, place, and social location.

A LIFE COURSE THEORETICAL FRAMEWORK FOR ANALYZING VARIATION IN FAMILY LIVES
Figure 1 re-organizes and extends core principles of the life course paradigm by specifying (1) possible interacting relationships between predictors and (2) family life course outcomes on different levels of analysis.We distinguish the macro, meso, and micro levels, which broadly resonate with the core principles of time and place, linked lives, and agency in Elder et al. (2003) and the dimension of "levels" in the life course cube (Bernardi et al., 2019).
F I G U R E 1 A theoretical framework for analyzing family life courses.
Our theoretical framework is situated in the tradition of methodological individualism.It proposes a life course elaboration of the prominent "Coleman boat" (Coleman, 1990) to account for family life course variation by time, place, and social locations and might be thought of as a "life course boat" that could be adapted to other field of application beyond family lives.We make two key adaptations to the generic principles of the life course paradigm.First, we assume that time, place, and social location jointly shape relevant conditions on the macro, meso, and micro levels and direct attention to cross-level interactions between the predictors (left-hand side of Figure 1).Second, we specify life course outcomes as unfolding over time as individuals age at the individual, relational, and population levels, which are linked to each other through aggregation processes (right-hand side Figure 1).Age as the central individual-level timeline expresses the basic premises of the life course paradigm that highlight the social and personal meaning attached to age (Mortimer & Shanahan, 2003).
The dotted arrow at the top of Figure 1 illustrates that one birth cohort's population-level family life course outcomes shape contextual conditions and family life course norms as relevant macro-level predictors for succeeding birth cohorts (Easterlin, 1976;Ryder, 1965).Next, we elaborate on each of these two adaptations before explicating the added value of the proposed framework to general principles of the life course paradigm and adjacent theoretical accounts on global family change (GFC; Furstenberg, 2019;Pesando, 2018) and the theory of conjunctural action (TCA; Johnson-Hanks et al., 2011).

Time, place, and social location: Interacting relationships between predictors
Family life courses vary across time, place, and social location because these factors jointly determine relevant predictors on the macro, meso, and micro levels and their interactions.Time here refers to cohort and period differences, place to regional variation, and social location to possibly overlapping categories of social (dis-)advantage, prominently education, social class, gender, race-ethnicity, or sexual orientation.Contextual conditions to which people are exposed depend on the time and place in which they live and their social location.For example, a woman coming of age in the early 20th century would not have access to hormonal contraception to plan the timing and spacing of births.However, in the late 20th century, she mightdepending on her place of residence, education, and economic resources.
We place social location on the same level of abstraction as time and place because family life courses can vary just as much between social groups as between cohorts and regions and social location features prominently in many theories of family change.The aim of our framework is to aid hypotheses on family life course variation on the three key dimensions of time, place, and social location.Nonetheless, social location is analytically distinct from time and place to a certain extent because (1) the relevant categories of social location vary across time and place, and (2) social location will typically alter the implications of macrostructural contexts that individuals who were born in the same time and place share (see quantitative example application in Family Life Course Change between Baby Boomers and Millennials section below).
Macrostructural conditions that are particularly relevant to variation in family life courses include economic opportunities (e.g., the kind of employment available), institutional characteristics (for instance, family laws and policies and access to social protection), the prevailing family ideology and cultural schemas, and access to technology (see also Furstenberg, 2019).These macro-level factors, in turn, affect meso-level networks of linked lives such as (extended) families, peer groups, and religious communities that impact the family behavior of their members, for example, through social control and role modeling (Bernardi et al., 2007;Roy & Settersten Jr., 2022).Finally, individual agency is nested within a macro-level opportunity structure and meso-level networks.Agency here refers to the individual values, capacities, choices, and behaviors that affect family outcomes (Heckhausen & Buchmann, 2019;Heckhausen & Schulz, 1995).As illustrated with the return arrows on the (figure 1) left side, individual agency shapes meso-level networks.Through aggregation, agency, and networks contribute to shaping macrostructural contexts, for example, by defining opportunity structures in partnership markets.
A large body of research documents the direct effects of predictors on different levels of analysis on the probability of experiencing specific holistic family life courses and their constitutive components, that is, the timing and sequencing of family events over the life course.In addition, our framework draws attention to possible interacting relationships between predictors of family life course variation.We distinguish (1) preconditioning, (2) reinforcing, (3) counteracting, (4) precluding, and (5) alteration as possible interacting relationships between predictors on the same or different levels of analysis.

Preconditioning
Preconditioning implies that one predictor must be given for another predictor to be activated.For example, anthropological research on fertility in West Africa shows that a cultural schema termed "numeracy of children" has to be present before women purposefully limit and delay fertility in favor of educational attainment and career advancement (Bledsoe, 1990; see qualitative example application below).Another prominent example is the "marriage bar," the economic preconditions deemed necessary for realizing intentions for marriage and parenthood, which can differ between cohorts by gender or racial groups (Lichter et al., 2002;Sweeney, 2002).

Reinforcing
Reinforcing relationship denotes that two predictors reinforce each other in favoring the realization of specific family life courses.For example, meso-level mechanisms of social control in families and local communities typically reinforce cultural taboos against divorce or homosexuality.Especially in countries with weak state and labor market institutions, extended kinship networks and local religious communities take strong norm-setting and norm-enforcing functions that can reinforce dominant cultural schemas, not least because these networks provide an economic safety net.

Counteracting
Counteracting relationships between predictors denote that the presence of one predictor reduces the impact of another in bringing about specific types of family life courses.For instance, the global diffusion of Western values that normalize small nuclear families and alternative family forms might initially be counteracted by social control mechanisms in mesonetworks of extended families that seek to uphold traditional cultural schemas of high fertility and universal marriage.Together, reinforcing and counteracting predictors are thus likely to shape the pace of family change, that is, family life course variation across cohorts, in possibly nonlinear and fluctuating ways.

Precluding relationships
Precluding relationships denote that one predictor's presence nullifies another's impact.For example, the lack of a suitable partner can nullify the positive impact of generous parental leave policies on highly educated women's probability of realizing fertility intentions (see Aisenbrey, Evertsson, & Grunow, 2009).The lack of a suitable partner then precludes the intended effects of social policies on family life courses (Jalovaara & Fasang, 2020).Similarly, biological infertility will preclude a range of other predictors from shaping the timing and spacing of fertility.Legal regulations, for instance, banning abortion or criminalizing unmarried cohabitation, will further preclude other predictors, such as egalitarian gender values, from shaping family life courses.

Alteration
Alteration denotes an interacting relationship between predictors where the presence of one predictor qualitatively changes the impact of another.For example, the diffusion of online dating (technological change) altered individual partner selection strategies (agency) over the life course.Through online dating platforms, hierarchies of the desirability of partners become more apparent, prompting individuals to seek partners who are more desirable than themselves (Bruch & Newman, 2018).The online dating process also creates different, clearly marked stages in initial partnership formation compared with mating processes in the "real" world, with different selection rules at each stage: browsing, viewing, and writing to potential partners (Bruch, Feinberg, & Lee, 2016).
Alteration is specifically relevant to family life courses because they typically consist of trajectories of categorical qualitative states, such as being single, childless, or divorced with stepchildren.Preconditioning and precluding relationships between predictors define whether a specific association between the predictors and the outcome occurs at all or not, conditional on the presence of another predictor.Reinforcing and counteracting relationships are a matter of degree, where the joint presence of two predictors increases or decreases the prevalence of specific family life courses to a greater extent than if one predictor was present alone.In addition to dichotomous either-or relationships and relationships of degree, the joint presence of different predictors can completely alter the types of mechanisms that operate and give rise to qualitatively different family life courses.The five relationships described above are not nonexhaustive; additional relationships might be important for specific research questions about family life courses.
To date, family life course research has devoted little attention to quantifying the relative importance and disentangling interactions between predictors on the micro, meso, and macro levels in different historical and social contexts.In some contexts, family life courses might be primarily driven by individual agency, while in others, regulative macrostructural conditions are more critical.An example of the latter is China during the one-child policy, which channeled individuals into a restricted set of permitted family life courses regardless of social networks or individual preferences.Individual agency likely more significantly impacts family life courses in societies with mature welfare states, high levels of prosperity, and liberal social norms, leading to destandardized family life courses.Such settings would require individuals to become more "agentic" and make active choices about life goals, which are not perceived as optional elsewhere.Economic prosperity, the rule of law, and liberal norms thus become preconditions for individual agency to strongly impact family life course outcomes (Figure 1).Conversely, in resource-constrained contexts with ineffective governments and limited welfare provision, extended families and local (religious) networks likely restrict individual agency and reinforce the formative impact of prevailing normative schemas on family life courses.

Family life course outcomes
A life course outcome has to span at least two time points, taking the transition from one state to another as the smallest temporal unit.Typically, a life course theoretical (LCT) framework should predict outcomes that unfold over more extended periods and arise from multiple family events' combined duration and sequencing (Figure 1).

Individual family life course outcomes
Individual family life courses denote the combined timing and sequencing of multiple family states across the life course (Figure 1).The absence of family events over extended periods is a particularly interesting feature that can only be detected by focusing on the combined absence of multiple events, for example, enduring single childlessness into mature adulthood (Jalovaara & Fasang, 2020).Which family states matter, for example, marriage or multigenerational living arrangements, varies across time, place, and social location, and the selection of relevant states has to be guided by theoretical considerations (Trask, 2018).Interrelated events in multiple life domains, especially work and family lives, can mutually condition and constrain each other (Fasang & Aisenbrey, 2023).Because family life courses unfold as individuals age, and age has both personal and social meaning, our theoretical framework is firmly rooted in the tradition of methodological individualism (Coleman, 1990).Unlike households or family networks that have shifting members and change their composition over time, individuals are durable units of analysis, even if they are embedded in different family configurations.

Relational family life course outcomes
Relational family life course outcomes denote characteristics of family life courses on the dyadic or social network level that take dyads, triads, or small groups as units of analysis (Figure 1).Relational family life course outcomes include dyadic similarity between parents' and children's family life courses to assess the intergenerational transmission of family life course patterns (Fasang & Raab, 2014), or fertility timing (Morosow & Trappe, 2018).Other applications have assessed family life course similarity within sibling dyads to illuminate family-of-origin effects (Raab et al., 2014).Whereas family dyads are defined by biological relationships that only end through the death of one dyad member, relationship dyads can also end through separation.Individuals, therefore, typically contribute to multiple parallel and consecutive dyads in relational family life course outcomes.The dyadic similarity between spouses' work trajectories, for example, after the birth of a child, zoom into the joint timing and sequencing of work and family life courses (Nutz & Gritti, 2022).In qualitative analyses, longitudinal couple interviews can be used to capture relational family life course dynamics (Bernardi, 2021).Quantitative studies have used dyadic sequence analysis or event history models, where the strength of the association between a focal person and a network member becomes the relational outcome (Buyukkececi et al., 2020;Pink et al., 2014).Relational family life course outcomes must be explained with dyadic predictors and not just the individual characteristics of each dyad member.For instance, the gender constellation of a given dyad will be the relevant predictor of sibling similarity in family life courses, not one sibling's gender alone.Relational family life course outcomes capture a new relational property of a dyad or small social network and do not arise from simple aggregation processes (Marsden, 2024).However, events in each dyad member's family life course can affect the other dyad member, suggesting a continual interplay between close network members' life courses.

Population-level family life course outcomes
Population-level family life course outcomes arise from aggregating individual family life courses and their relational properties within meaningful population units typically defined by time (cohort), place, and social location (Figure 1).Prominent population-level outcomes include family life course typologies that exist under different structural conditions (e.g., Elzinga & Liefbroer, 2007;Gruijters et al., 2023), the degree of standardization of family lives (Billari, 2001;Zimmermann & Konietzka, 2018), the convergence or divergence of life courses across birth cohorts (Liao & Fasang, 2021), family life course stratification by gender, race, or education (Fasang & Aisenbrey, 2022;Madero-Cabib & Cabello-Hutt, 2022), or population level associations between life domains, such as work and family lives (Piccaretta & Elzinga, 2014).
Institutionalist life course approaches (Kohli, 2007;Mayer, 2004) assume that given combinations of legal, normative, and structural conditions channel individuals into a few possible and likely family life course types while hindering other theoretically possible types that do not occur empirically.Sequence and cluster analysis typically assess family life course typologies (Studer, 2013).Because family life courses consist of trajectories of qualitative categorical states and not metric outcomes, the typology approach is particularly useful, including visualizing family life course typologies.Parents' typical family life courses can take a norm-setting function for the next generation when children shape their own intentions relative to what they observe in their parents' generation (dotted arrow, Figure 1).
Life course (de)standardization-the degree to which life courses become more or less similar regarding the timing and sequencing of family states across cohorts-is a central population-level outcome in comparative life course research and family demography (Brückner & Mayer, 2004).Destandardization is typically assessed by comparing pairwise distances between life course sequences or the number of prevalent family life course types.The social stratification of family life course typologies by gender, race, education, or social class has received less attention than destandardization.However, family life course stratification is central to informing theories of diverging destinies (McLanahan, 2004) and bridges into the family policy field by identifying which family lives are associated with the highest poverty risks in different welfare states (Fasang et al., 2024;Zagel & Van Winkle, 2022).Similarly, to date, we know little about how the strength of associations between work and family lives varies across social groups that face varying contextual conditions (Fasang & Aisenbrey, 2022).

Added value to the general life course paradigm
The added value of our LCT framework to the general life course paradigm is that we aim for complexity reduction and unpacking the specificity of family life course variation to given contextual conditions.
First, to reduce complexity, unlike the general life course paradigm, our theoretical framework conceptualizes key dependent variables for constructing hypotheses on family life course variation on the individual, relational, and population levels, along with guidance on measuring and empirically analyzing them.The commitment to methodological individualism separates our approach from other outcome conceptions in the life course field, such as "family life cycle" models on the family level (Glick, 1977;O'Rand & Krecker, 1990) and "life stages" (Johnson-Hanks, 2002).Family life cycle models promoted Western-centric normative conceptions of nuclear families that were increasingly empirically inaccurate (Konietzka & Kreyenfeld, 2021).In our framework (Figure 1), normative ideas about which types of transitions should be made in different "life stages" are considered macro-level predictors of individual family life courses.Related concepts of "life span" in psychology and "life cycle" in economics are also located on the individual level but differ from "life course" in important respects that make them less suitable for analyzing family lives.Key concepts of growth and decline in life span psychology, or accumulation and depletion in life cycle economics, have no natural application to family life courses.
Second, to unpack the specificity of family life course variation to sociohistorical locations, our framework identifies possible interacting relationships between predictors and draws attention to social location as an additional key dimension of family life course variation.The general life course paradigm remains vague about the relative importance of different predictors (time, place, linked lives, agency) in generating family life courses and how the empirically most predictive determinants might interact to shape the observed outcomes.Our framework specifies key interacting relationships between predictors that allow theorizing their relative importance under different conditions.Finally, the social stratification of family lives is a key interest in family research but is often neglected in general life course approaches focusing on age stratification and human development (Fasang & Mayer, 2023).Social stratification by class, gender, or race/ethnicity does not feature prominently in the general principles of the life course paradigm (Elder et al., 2003) or the life course cube (Bernardi et al., 2019).Our framework (Figure 1) highlights family life course stratification as a key population-level outcome and defines social location as a central dimension of family life course variation.

Added value to adjacent theoretical approaches
Theories of GFC and the TCA arguably operate on similar levels and follow overlapping goals with our LCT framework.

Global family change
Theories of GFC, rooted in historical demography, have recently gained momentum with renewed efforts to leverage globally available data, including on low-and middle-income countries, to map global family variation (Furstenberg, 2019;Pesando, 2018).Like the GFC approach, our framework seeks to specify predictors on different levels of analysis relevant to family life courses globally, and not only in affluent countries of the global North.Focusing on individual trajectories and the commitment to methodological individualism sets our approach apart from recent studies on global variation in aggregate family configurations that use multidimensional indicators of family situations (e.g., our theoretical framework still places individuals' relationships center stage in conceptualizing relational family life course outcomes while keeping the individual as an analytically and empirically tractable anchor).In addition, our framework seeks to systematically disentangle interacting relationships between predictors of family life courses to identify the relative importance of different predictors under varying conditions (Figure 1).Finally, the GFC approach naturally takes a large-N comparative approach to map global family change.In contrast, our framework, rooted in methodological individualism and differential life course sociology, suggests single-country case studies or small-N designs to disentangle interacting relationships between predictors within specific contexts.

Theory of conjunctural action
The TCA (Johnson-Hanks et al., 2011) is rooted in life course anthropology and has gained considerable traction over the past decade.In our framework, the combined and interacting predictors displayed on the left-hand side of Figure 1 make up the situational "conjuncture," which is construed into channeling individual action in TCA.Our approach shares many basic premises of TCA, including the attention to life course dynamics and path dependency and the joint imprint of contextual conditions on key family and interrelated work events.Within generally similar premises, our framework places a different emphasis than TCA in two respects.
First, by highlighting specific types of interacting relationships between predictors, we propose to unpack the black box of situational "conjunctures," which can be understood as many-fold interactions between all contextual and individual conditions present at a given instance.Our framework suggests reducing the contextual complexity subsumed in "conjunctures" in favor of theorizing the specific interacting relationship between a reduced set of dominant predictors that empirically strongly predict family life course outcomes.Second, instead of focusing on individual action in specific family events, we specify key outcome concepts on individual, relational, and population-level family life courses (see Alber, 2023).Finally, we follow a narrower goal of adapting generic life course principles to the sociological and demographic study of family life courses rather than specifying a general theory of action and ensuing population patterns as proposed in TCA (Huinink, 2012).

EXAMPLE APPLICATIONS Family life courses in Senegal
The first case study illustrates how our framework (Figure 1) can be applied to study women's family trajectories-the timing, spacing, and number of births-by educational level in Senegal.As in most African countries, education is associated with lower fertility in Senegal.Women who completed secondary school have 2.3 children on average, compared with 5.1 among less educated women (Corker et al., 2022, p. 856).Family scholars have proposed several theoretical mechanisms to explain this phenomenon but disagree about their relative importance (Axinn & Barber, 2001;Bongaarts, 2010;Liu & Raftery, 2020).
First, ideational theories suggest that education creates a preference for smaller families, for example, through the spread of Western family norms and the weakening of traditional pronatalist beliefs ( preference change hypothesis).Second, education improves women's economic resources and power relative to their husbands and in-laws, as well as their knowledge of and access to contraception, which enables them to enact their desire for lower fertility (empowerment hypothesis).Third, education increases the perceived (opportunity) costs of having children.Educated women have better social and economic opportunities outside their homes, which are incompatible with having many children.Moreover, they generally want their children to attain advanced levels of education, which increases the costs of raising them (cost hypothesis).Finally, women tend to postpone marriage and childbearing to complete their education, leading to a delay in age at first birth with higher education.Women who start having children later tend to have fewer children overall, possibly with shorter spacing between them ( postponement hypothesis).
The four hypotheses are broadly related to the four dimensions of agency listed in Figure 1 (values, aspirations, capacity, choices, and behavior).In addition to individual agency, our framework draws attention to macrostructural contexts and meso-level networks.Senegal is characterized by religious high fertility schemas rooted in moderate Islam.Welfare benefits are marginal, and over 90% of work is concentrated in the informal sector.As a result, extended coresidential families and local religious communities function economic safety nets and take strong norm-setting and norm-enforcing functions that enact tight social control.Anthropological research in West Africa has shown that strong religious high fertility norms are associated with a lack of a "numeracy of children" schema.Children are seen as a gift of God, and women do not conceive of fertility as something that they can or should control (Bledsoe, 1990).Our framework suggests that social control in meso-level networks and the normative schema that "family formation is up to God's will" reinforce each other in counteracting the preference change and empowerment hypotheses jointly (see Figure 2).
Research on education and fertility is dominated by quantitative studies, which can only provide indirect evidence for the four hypotheses.We conducted in-depth interviews with 24 young Senegalese women between 2021 and 2023 in two rounds of interviews by a team of Senegalese interviewers switching between French and Wolof, the local language in Senegal (the interviews were conducted as part of the project "High Hopes and Broken Promises: Young Adult Life Courses in Senegal," which was funded by the German Research Foundation within the SCRIPTS Cluster of Excellence.See https://www.scripts-berlin.eu/research/researchprojects/General-Research-Projects/high-hopes-and-broken-promises/index.html for more details.Respondents were recruited through a snow-ball sampling starting in the interviewers' networks covering Dakar, rural regions, and smaller towns in the vicinity of Dakar yielding a relatively balanced sample in terms of gender, education and rural/urban location.The transcribed interviews were analyzed with qualitative content analysis using MaxQDA).
We found little evidence for the preference change hypothesis, which is consistent with our expectations that religious high fertility norms are reinforced in social networks to counteract a conscious wish and plan for fewer children (see Figure 2).In line with strong religious high fertility schemas, fertility intentions were universally high and did not vary by education.Most of our respondents wanted at least four children.The main reason was the overwhelming importance of religion as a driver of fertility preferences, as illustrated by the response, "I don't calculate.I don't limit myself also after all, I am a Muslim.So I don't limit the followers of Prophet Muhammad (peace be upon him)" (Fatima [fictitious names are used to ensure anonymity], 22, tertiary education).Some women even expressed pressure not to have a preference: "My values and principles do not allow me to pronounce on these two questions [number and timing of children], I prefer to leave everything in the hands of God" (Nancy, 35, no education), which was equally prevalent among lower and higher educated women: "I'll leave in God's hands what God grants me" (Mary, 25, tertiary education).
In contrast to fertility intentions, realized fertility varied by education, with highly educated women often remaining childless into their late 20s and 30s in line with the postponement hypothesis.While strong religious norms mandated universal high fertility intentions, education afforded greater social acceptance of delaying family formation in family networks: "If I had not gone to school, my parents would not have accepted that I was not married until now" (Ndoumbe, 23, tertiary in progress).Rather than an intrinsic desire for small families (preference change hypothesis), educated women often mentioned their ambitions for their children, in combination with the cost of educating them, as the main factors limiting their fertility, in line with the cost hypothesis: "What is important is that they grow up with a lot of success even if they are only two" (Aissa, 22, tertiary education).This is consistent with the idea that education shifts the "quantity-quality tradeoff" in fertility decisions (Axinn & Barber, 2001).Other explanations for opting for smaller realized family sizes referred to the opportunity cost of having children: "But if I wanted to have more than three or four children, because pregnancy is difficult, taking care of a child with all that it requires (…) time no longer allows it because every day you go to work" (Mariam, 36, secondary).The latter statement also highlights the interaction between work and family trajectories, an essential feature of life course outcomes in our framework that was perceived as particularly salient for their generation by our respondents: "Times are hard, we can no longer combine work and many children.You know it better than I do, the world has changed."(Aissatou,31,tertiary in progress).Mariam and Aissatou perceived having a large family and working to make a living as competing alternatives.
Our findings supported the idea that social networks reinforce strong religious high fertility schemas to counteract an educational gradient in preferences for smaller family sizes across the life course.Education did not impact fertility via changing preferences.In contrast, the cost of providing for children and the opportunity costs of childbearing featured prominently in educated women's explanations for delaying and reducing fertility.Education seems to impact women's fertility across the life course through material considerations and the synchronization with work lives rather than through ideational change.Our framework, in this case, was conducive to disentangling how predictors on the macro and meso levels reinforce each other in counteracting the preference change mechanism attributed to education in Western contexts.Aggregated to the population level, the educational gradient in individual family life courses suggests family life course stratification in which educated women have family trajectories of delayed parenthood and lower lifetime fertility, which could easily be tested with populationrepresentative data.Several macrostructural and ideational changes reshaped American society between the two generations.Economically, deindustrialization, skill-biased technological change (SBTC), and the rise of the service economy led to a decline in secure and well-paying blue-collar jobs.In contrast, low-paid service occupations proliferated (Autor & Dorn, 2013).SBTC increased economic returns to specific skill sets amidst declining returns to higher education.These trends fueled a polarization between "good" and "bad" jobs, with rising wage inequality and increasing economic insecurity, especially for the lower educated (Acemoglu & Autor, 2011;Kalleberg, 2011).

Family life course change between baby boomers and millennials
Economic restructuring, increasing economic insecurity, rising student debt, and a shift towards postmaterial values (Lesthaeghe, 2014) likely led to a decline in marriage and the rise of non-normative family types among Millennial cohorts compared with Baby Boomers (see Figure 3).Returning to or remaining in the parental home will be more prevalent as Millennials struggle to meet the "marriage bar" (Smock & Schwartz, 2020), resulting in a decline in marriage and a rise in non-normative family life course types.Due to job polarization, SBTC, and declining returns to education, marriage is reserved for smaller groups of affluent Millennials (Gruijters et al., 2023).In sum, due to the stratified rise of non-normative family life course types, family life courses will be more destandardized among Millennials than among Baby Boomers (Destandardization hypothesis).
Our framework draws attention to the differential experience of these structural changes by individuals in different social locations, defined by race, gender, and class.We focused on race in this illustrative example.We formulated competing hypotheses on how macrostructural changes might interact with race to impact generational change in family lives differently for Black and White Americans (Figure 3).On the one hand, Black Americans are historically concentrated in lower socioeconomic positions and, therefore, might be most exposed to adverse structural developments.As a result, generational change might be most pronounced for this group, suggesting a reinforcing relationship between adverse macroeconomic changes and reduced marital options for Black Millennials.In contrast, White Millennials might be more sheltered from adverse economic conditions because of their family resources and generally favorable socioeconomic position that counteract the impact of macroeconomic changes on their marital options ( greater exposure for Black Millennials hypothesis).In this case, among Black Americans, we would expect a larger increase in non-normative family life course types, resulting in a more substantial increase in destandardization between the two generations.
On the other hand, Black Americans were already most concentrated in economically insecure sectors among the Baby Boom generation and many generations before.Partially because of this, the decline of marriage was early and profound among this group (Raley et al., 2015).Akin to floor effects, adverse generational change might be attenuated because many already had "little to lose" among the Baby Boomer generation (attenuating/counteracting relationship between macrostructural changes and marital options for Black Millennials).For White Americans, in contrast, family change started later in the 20th century, with increasing marital instability and lower rates of marriage among those with lower levels of education, delays in marriage and fertility, and increasing levels of cohabitation among the highly educated (Bloome & Ang, 2020).Labor market polarization, which reduced the number of mid-skilled jobs typically occupied by Whites, might have reinforced these trends, leading to a stronger increase in the prevalence of non-normative family life course types and hence a greater destandardization among White Americans ( greater exposure for White Millennials hypothesis).
To leverage the empirical evidence against these two competing hypotheses, we conducted sequence and cluster analysis using the Dynamic Hamming Distance (Studer & Ritschard, 2016) for the entire NLSY population and White and Black American separately, and partitioning around medoids cluster analyses with state-of-the-art cluster cut-off criteria (Studer, 2013).Destandardization was measured with average pairwise sequence distances in each generation by racial groups.All analyses were weighted with the NLSY longitudinal and cross-sectional weights.
Table 1 presents average sequence distances by generation and racial group.Findings overall supported the destandardization hypothesis.The mean sequence distances between family life courses of Baby Boomers were 584.9 compared with 656.9 among Millennials.In line with the "greater exposure of White Millennials hypothesis" family life courses were already as destandardized among Black Baby Boomers as they were for White Millennials.Between generations, destandardization increased far less at 4.9% for Black respondents compared with 13.6% for White respondents.
State distribution plots of life course typologies (available from authors) underscored the rise of "non-normative" family patterns for Millennials, with substantial differences by race.Family life course types dominated by "married parenthood" were only experienced by 38% of Black Baby Boomers but 61% of White Baby Boomers.The family life course typologies for White and Black Millennials showed a delay and decline of marriage and a rise of nonnormative family life courses compared with Boomers, especially for White Millennials compared with White Boomers.For both Black and White Millennials remaining in the parental home for extended periods, cohabiting parenthood, extended singlehood, and single parenthood became more common.Among White Millennials, 39% experienced family life course types of stable marriage with children (a drop of 22 percentage points relative to their parents), but a similar share of Black Millennials and Black Baby Boomers lived family life courses characterized by stable marriage.Generational change in the rise of non-normative family life course types was thus far more pronounced for White than for Black Americans, supporting the "greater exposure of White Millennials hypothesis."This illustrative example application focused on interactions between structural economic changes and race as an indicator of social location.The framework could easily be extended to incorporate ideational change and changes in gender roles to assess how they interact with various indicators of social location (Goldscheider et al., 2015).

CONCLUSION
The usefulness of the life course paradigm for guiding hypotheses on variation in family life courses has been limited by its broad and abstract principles and heuristics, highlighting rather than reducing complexity and searching for generalizability rather than specificity.This contribution aimed at filling the basic heuristics of the life course paradigm with substantive content to specify how macrostructural conditions, meso-level networks, and dimensions of individual agency might interact to affect family life course variation across time, space, and social location.Theoretically specifying and empirically analyzing the interactions between predictors at different levels and precisely quantifying their relative importance in different global settings would be promising to advance life course theory, inform social policies, and counter the Western bias in life course sociology.
Building on Coleman (1990), we proposed a "life course boat" specifically adapted to family life course variation.The notion of a "life course boat" could easily be transferred to other fields of application, such as work lives or migration trajectories, with some adjustments to account for the specific nature of these life course processes as outcomes on different levels of analysis, as well as the mechanisms that generate them.For instance, unlike family life courses that consist of qualitative categorical trajectories on the individual level, work life courses can also be conceptualized as trajectories of metric outcomes, such as earnings volatility or wealth accumulation.This would need to be considered in the specification of work life course outcomes on different levels of analysis in a "life course boat." The life course approach is intrinsically comparative.Theory-guided most similar versus most distinct case designs focusing on different phases of family life courses can be particularly informative in our framework.Small-N country and cohort comparisons may often be better suited than large-N comparisons to do justice to the sociohistorical specificity of birth cohorts and disentangle interacting relationships between predictors (Brückner & Mayer, 2005;Fasang, 2012).Large-N cohort and country studies remain a necessary first step of discovery to map variation in family life courses (Pesando, 2019) that can inform more explanatory analyses in targeted small-N comparative designs.Experimental designs and potential outcomes frameworks of causal inference do not naturally transfer to family life course studies for ethical and practical reasons.Instead, causal hypotheses that link predictors and temporal features of family life courses will often rely on targeted comparative designs and sophisticated longitudinal descriptions to assess in an implication-based manner whether evidence is in line with or contradicts a causal argument.Precise theoretical reasoning on causal mechanisms is paramount to leverage longitudinal descriptive evidence against their predictions.Our conceptualization of family life course outcomes could also be helpful to group relevant studies on similar outcomes for meta-analyses of existing, often strongly exploratory studies on family life course variation.
We hope that separating the basic heuristics of the life course paradigm into interacting predictors and family life course outcomes on the individual, relational, and population levels can further our understanding of family life course variation.Developing narrower mid-range theories that fill the basic life course principles with substantive content and target specific fields of application is promising to advance life course theory.
Our second illustrative example compared Black and White Americans to assess family life course change between two birth cohort groups in the United States to focus on how similar macrostructural changes differentially affect family life course change by social location, in this case, race.We used data on family life courses between ages 18 and 35 from the National Longitudinal Survey of Youth (NLSY).The first cohort, born 1957-1964, was part of the late "Baby Boomer" generation who experienced their active family formation in the 1980s and 1990s.The second cohort consisted of early "Millennials" born 1980-1984 between ages 18 and 35 from 1998 to 2020 (seeGruijters et al., 2023 for more details on the sample).F I G U R E 3 Racial differences in family life course change between Baby Boomer and Millennial cohorts.
T A B L E 1