According to recent UN estimates, some 304 million individuals (about 3.7 percent of the world’s population) are international migrants, defined as people who live outside of their country of birth (United Nations, 2025). While this is a significant number, the most common form of migration globally in fact takes place within countries (Niva et al. 2023) and is referred to as internal migration.
Discourses on migration, whether internal or international, are often framed similarly: “migrants seek a better life for themselves and their children”; “migrants lift themselves by their bootstraps”, etc. The need to understand what factors drive voluntary migration may be especially acute in transitioning economies (Bell et al 2015). In these societies, migration is likely to grow in importance as fertility and mortality rates stabilize at lower levels and economic and social transformation generate rural-to-urban relocation. 

True grit

In a recent paper (White et al. 2024), we look at evidence on the question of whether migrants have more “grit”, i.e. motivation, wherewithal, and gumption than those who stay behind. This touches on an age-old demographic question of whether migrants are a select group of individuals, that is, whether those who migrate are different from those who do not in domains such as health, finances, and education.
In the last several years, demographic research on migration has expanded to include additional measures to shed light on migration motivation. Some of this work has suggested that aspects of personality may matter in taking the decision to migrate (Bernard 2022). Grit—irrespective of other seemingly success-linked characteristics such as education and occupational skills—may foreshadow who migrates and how well migrants do at destination. We argue that grit and its associated measures capture non-cognitive characteristics that affect motivation, risk assessment, and perseverance. With such measures in hand, multidisciplinary research can provide greater insight into migrant selectivity and subsequent socioeconomic outcomes.

Why do we care? Policy 

This all matters because policies at the local, regional (provincial), and nation-state level often seek to attract or discourage migrants, even internal migrants. While much discourse focusses on international migrants (Lancet 2025), internal migration processes also face varying policy incentives and disincentives, ranging from distaste for rural influx in urban areas to programs subsidizing certain locations to make them more attractive to new arrivals. More tolerance toward migrants, even if not arriving from privileged geographic origins or social backgrounds, may make their arrival not such a bad gamble after all.

Empirical evidence

We seek evidence on the influence of grit—here a measure of perseverance in the face of adversity—on internal migration behavior in South Africa. Using two waves of data from a longitudinal survey of a rural-origin population in South Africa (the Migrant Health Follow-Up Study, MHFUS), we test whether a composite psychosocial index of grit (Duckworth, et al 2007) predicts internal migration, net of conventional measures such as age, sex, and education. Simple bivariate correlations point to a strong association between migration and grit for both males and females. The question remains whether this relationship holds when adjusting for other conventional predictor variables.
We examine whether young adults are more likely to move out of their rural-origin community (hence “migration”), a district-sized area of about 100,000 persons within a former Bantustan (homeland) occupied by xi-Tsonga-speaking Black South Africans. Most who migrate head for the heavily urbanized Gauteng Province (containing the major cities of Johannesburg and Pretoria) or for intermediate small to medium towns. Our statistical models consider two distinct dependent variables:

1) whether the individual is a “migrant” and, separately,

2) the number of reported places already lived.

Both dependent variables are made a function of fixed variables and other personal characteristics (including the “grit index”) measured at an earlier point. We employ sequential regression models, adding other covariates to see how much the apparent influence of grit is altered by their addition.
Figure 1 summarizes how well grit predicts migration for males and females separately across the two migration outcomes, using four progressively more comprehensive models. When grit is the only predictor in the equation, it is highly significant for both men and women, and for both migration indicators. It still shows through—albeit to a lesser extent—when age and education (model 2), then also health and origin community (model 3) are added. Most interestingly, the progressive inclusion of these variables serves to reduce the grit effect more for males than females, even pressing the former to non-significance, when prior migration experience (already a migrant two years prior, model 4) is added. 

What differs here is the interplay of the mix of characteristics and individual histories. Age, education (especially completing secondary school in this rural-origin population), and prior migration predict migration for both males and females, as is generally the case in migration studies. Yet, the influence of grit shows through more powerfully for women, albeit reduced appreciably in magnitude, in the presence of these other factors. 

Conclusion 

Where does this leave us? While conventional demographic models of internal migration continue to capture key elements of (voluntary) movement, there is room to expand our portfolio of characteristics understood to influence migration. Measurement will be a challenge, given the difficulty of assessing these typically unobserved variables and their potential fluctuation over the lifetime. Nevertheless, the importance of migration in redistributing labor and enabling socioeconomic advancement for individuals and their families argues for pushing harder in depth and breadth to understand personal and societal factors that spur or deter geographic movement. Policies narrowly tailored to manifest demographic and skill indicators may underestimate the contributions of other highly motivated individuals.
The gender differential we find deserves particular consideration. While scholarship has often emphasized male migration, even arguing its normative nature in some regions, the increasing attention to female participation in labor markets and migration warrants further examination. Perhaps female migrants are more selective along characteristics such as grit, as they face greater structural barriers and constraints (e.g. employment practices and family expectations). Expanding the view of the migratory process may help explain why some move while others stay behind. 

Acknowledgments

Funding for the underlying research was provided by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NIH 1R01HD083374; NIH P2CHD041020). The MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt) acknowledges funding from The Wellcome Trust, UK (grants 058893/Z/99/A, 069683/Z/02/Z, 085477/Z/08/Z, 085477/B/08/Z); the Medical Research Council, South Africa; and the South African Population Research Infrastructure Network hosted by the South African Medical Research Council.

References

Bell, M., Charles-Edwards, E., Ueffing, P., Stillwell, J., Kupiszewski, M., & Kupiszewska, D. (2015). Internal Migration and Development: Comparing Migration Intensities Around the World. Population and Development Review, 41(1), 33–58. https://doi.org/10.1111/j.1728-4457.2015.00025.x

Bernard, A. (2022). Does the association between internal migration and personality traits hold in different countries? Journal of Research in Personality, 101, 104300. https://doi.org/10.1016/j.jrp.2022.104300

Duckworth, A., Peterson, C., Matthews, M., & Kelly, D. (2007). Grit: Perseverance and passion for long-term goals. Journal of Personality and Social Psychology, 92, 1087–1101. https://doi.org/10.1037/0022-3514.92.6.1087

Lancet. (2025). The uncertain future of migrant and refugee health. The Lancet, 405(10495), 2103. https://doi.org/10.1016/S0140-6736(25)01245-0

Niva, V., Horton, A., Virkki, V., Heino, M., Kosonen, M., Kallio, M., et al. (2023). World’s human migration patterns in 2000–2019 unveiled by high-resolution data. Nature Human Behaviour, 7(11), 2023–2037.

United Nations (Population Division) International Migration. (2025). https://www.un.org/development/desa/pd/content/international-migration-1. Accessed 30 May 2025

White, M. J., Myroniuk, T. W., Ginsburg, C., & Pheiffer, C. (2024). Do Migrants Exhibit More Grit? A Research Note. Demography, 61(5), 1309–1323. https://doi.org/10.1215/00703370-11577556

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Household structure and composition reflect the individual life trajectories of household members, who are often linked by family ties. Individuals may be born, or die, move in or out, and together they shape the living environment of young children. Children are dependent on household members for essential care, including economic support and socialisation. While this is often given by parents, other household members can also contribute to children’s wellbeing and survival. 

Household dynamics: a longitudinal perspective

Fluidity in households and their membership make it difficult to capture these features in quantitative analysis. Households can be defined as a status (sharing a homestead), or as a network through which support is transferred. Moreover, individuals are generally considered as members of only one household unit, though this is not always the case. Longitudinal data can help to capture shifting households, although a specific definition of “household” must be applied.

Health and Demographic Surveillance Systems (HDSS) provide an exceptional opportunity to examine these shifts in households in sub-Saharan Africa, because they “follow” populations within a geographically delimited region, recording the demographic events of individuals embedded in households, and making it possible to identify a household’s structure and composition at the time of any event (in contrast to only at the time of survey data collection).

Using de facto household membership (people living in the same residence), it is possible to follow the movements of individuals in and out of households, and to know household structure and composition at any given time (Menashe-Oren, Compaoré, et al. 2023). Figure 1 illustrates how a child may experience multiple changes in a household before reaching age five and highlights that the same structure (number of members) may correspond to different compositions (kin relationships).

In the rest of this article, we will consider the household structure and composition at the time of a child’s death.

The role of the household in child mortality

Child mortality remains high in sub-Saharan Africa as compared to other regions of the world: according to the UN World Population Prospects, the under-five mortality rate was 70.1 per 1,000 in 2022, whereas the second highest rate was 36.0 in Central and Southern Asia, and the lowest rate 3.5 in Australia and New Zealand. That said, important gains have been made in reducing child mortality in sub-Saharan Africa, thanks to multiple factors including improved infrastructure, better access to medical services and an increase in maternal education. 

Children’s survival can also be determined by the close social environment in which they live: the household. It is well established that the presence of a mother has a positive effect on child survival, while for fathers the evidence is varied (Sear and Coall 2011). Similarly, grandparental involvement, and particularly co-residence with a child can be important. 

Recent evidence using HDSS data from multiple sites in five countries in south-eastern sub-Saharan Africa (Ethiopia, Kenya, Mozambique, Tanzania, South Africa), displayed in Figure 2, indicates that for children aged under five, the presence of an older adult (65+ years old) in the household increases the likelihood of death by 23% in comparison to children in nuclear-type households (Menashe-Oren, Bocquier, et al. 2023). Rather than helping with care, older adults likely require care themselves, and resources need to be spread more thinly than in smaller nuclear-type households. However, this HDSS-based study was limited to examining household structure, without consideration for kin relations. 

In other work, also using HDSS data from three West African countries (Burkina Faso, Senegal and The Gambia), where relationships between individuals were taken into account, it was found that the association between an older adult in the household and child mortality depends on the older adult’s relationship to the child. In the case of a co-resident paternal grandfather, the risk of a child’s death is 25% higher, but with a co-resident maternal grandmother, the child’s survival chances increase by 50% compared to children not living with grandparents (Compaoré 2021). With the decline in adult mortality, the proportion of children living with grandparents (in three-generational households) has been increasing in many African countries since the 1990s, so this is a particularly important point to consider.

References

Compaoré, Y.  Dynamiques familiales et santé des enfants: perspectives longitudinales en Afrique de l’Ouest. UCL-Université Catholique de Louvain

Menashe-Oren, A., Bocquier, P., Ginsburg, C., Compaoré, Y., & Collinson, M. A. (2023). The dynamic role of household structure on under-5 mortality in southern and eastern sub-Saharan Africa. Demographic Research, 49 (Article 11), 249–294. https://doi.org/10.4054/DemRes.2023.49.11

Menashe-Oren, A., Compaoré, Y., Bocquier, P., & Ginsburg, C. (2023). Dynamic household structure and composition: a manual for longitudinal analysis of living arrangements. BMC Research Notes, 16(223), 1–6. https://doi.org/10.1186/s13104-023-06485-x

Sear, R., & Coall, D. (2011). How Much Does Family Matter? Cooperative Breeding and the Demographic Transition. Population and Development Review, 37 (SUPPL. 1), 81–112. https://doi.org/10.1111/j.1728-4457.2011.00379.x

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Mothers are important for under-five child survival, but so are siblings. The timing of sibling births, or birth spacing, is important, especially in low- and middle-income countries. Generally, an interval of at least 24 months between births is recommended, to avoid maternal depletion due to excessive “competition for care”, to allow sufficient breastfeeding time and to lower the risk of disease transmission.

To disentangle the effects of siblings and mothers on child survival, longitudinal data are needed. Covering diverse contexts across sub-Saharan Africa, and a large number of children under-five years old (~560,000), Health and Demographic Surveillance Systems (HDSS) provide a unique opportunity to explore these effects.

The confirmed role of mothers in child survival

The risk of child mortality depends on a number of maternal factors, including her age at childbirth, and her presence in the child’s day-to-day life. It is higher for mothers aged under 20 or over 36 at the time of the birth. Likewise, when a mother migrates and leaves her child(ren), her absence is associated with a higher risk of child death. This is probably because she is not present to provide direct care including breastfeeding, or to make sure her child follows immunization schedules. Potential financial benefits, through remittances, do not seem to be strong enough offset the negative effect of her absence.

While the absence of a mother due to migration increases a child’s risk of death by around 50%, her absence due to death increases the risk more than tenfold (Bocquier et al. 2021). The effect of maternal death is strongest in the 15 days preceding her death and the three months following it. This pre-death effect is explained by prolonged illness, in particular due to HIV or tuberculosis; in the final stages of disease the mother is usually less able to care for her child(ren) (Houle et al. 2015).

The unexpected role of younger siblings

Birth spacing with an older sibling has consistently been found to affect child survival, with intervals shorter than 36 months increasing the probability of infant and under-five death (Molitoris et al. 2019). However, based on the analysis of HDSS data, where precise timing of births is possible, recent research has found that birth spacing with respect to a younger sibling is even more important (Bocquier et al. 2021). The risk of child mortality is highest when a birth interval with a younger sibling is less than 23 months. However, when a mother is pregnant with the younger sibling, the risk of child death is actually lower (Figure 1). This beneficial period during pregnancy could be related to the antenatal care received by the mother and her visits to health facilities with her child. The child may be examined on these occasions, or the mother may receive general advice about healthcare for her children. The presence of the father in the household during the pregnancy may also be beneficial, through his direct role in childcare or in looking after the expectant mother. Additional care provided by other family members and friends may also have spillover effects on a child’s health.

Once born, the presence of siblings close in age can increase a child’s exposure to life-threatening communicable diseases. However, if the older sibling does not co-reside with the youngest child, this risk should be reduced and there should also be less competition among the children. However, the absence of an older or younger sibling due to migration is actually associated with a higher risk of mortality. This is likely a reflection of a dispersed, unstable, family unit. Furthermore, the death of a sibling is detrimental to child survival. Siblings share a risk of infectious diseases by living in the same environment. They receive similar levels of care from their parents, and they share a genetic background. Clustering of deaths within families is therefore likely (van Dijk 2018). As after a mother’s death, the risk of a child’s death is elevated before and after a sibling’s death. 

Policy implications

In addition to the known proximate determinants of child mortality, including maternal factors, risk factors associated with siblings deserve attention from healthcare providers. In particular, birth intervals of at least 24 months are recommended as they increase the survival chances of both older and younger siblings. The mother’s pregnancy appears to be beneficial for the survival of already existing young children, but things tend to change after delivery: for various possible reasons, the presence of a younger, closely-spaced child tends to be detrimental for older (but still very young) siblings. Finally, caregivers should pay special attention to children whose siblings do not co-reside with them, are sick or have died. Increased awareness of these risk factors associated with siblings could help reduce child mortality in sub-Saharan Africa. 

References

Bocquier, P., Ginsburg, C., Menashe-Oren, A., Compaoré, Y., & Collinson, M. (2021). The Crucial Role of Mothers and Siblings in Child Survival: Evidence From 29 Health and Demographic Surveillance Systems in Sub-Saharan Africa. Demography. doi:10.1215/00703370-9429499

Houle, B., Clark, S. J., Kahn, K., Tollman, S., & Yamin, A. E. (2015). The impacts of maternal mortality and cause of death on children ’ s risk of dying in rural South Africa : evidence from a population based surveillance study ( 1992-2013 ). Reproductive Health, 12(Suppl 1), S7. doi:10.1186/1742-4755-12-S1-S7

Molitoris, J., Barclay, K., & Kolk, M. (2019). When and Where Birth Spacing Matters for Child Survival : An International Comparison Using the DHS. Demography, 56(4), 1349–1370. doi:doi:10.1007/s13524-019-00798-y

van Dijk, I. K. (2018). Early-life mortality clustering in families: A literature review. Population Studies, 73(1), 79–99. doi:10.1080/00324728.2018.1448434

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