Sibling Configuration Predicts Individual and Descendant Socioeconomic Success in a Modern Post-Industrial Society

Growing up with many siblings, at least in the context of modern post-industrial low fertility, low mortality societies, is predictive of relatively poor performance on school tests in childhood, lower levels of educational attainment, and lower income throughout adulthood. Recent studies further indicate these relationships hold across generations, so that the descendants of those who grow up with many siblings are also at an apparent socioeconomic disadvantage. In this paper we add to this literature by considering whether such relationships interact with the sex and relative age of siblings. To do this we utilise a unique Swedish multigenerational birth cohort study that provides sibling configuration data on over 10,000 individuals born in 1915–1929, plus all their direct genetic descendants to the present day. Adjusting for parental and birth characteristics, we find that the ‘socioeconomic cost’ of growing up in a large family is independent of both the sex of siblings and the sex of the individual. However, growing up with several older as opposed to several younger siblings is predictive of relatively poor performance on school tests and a lower likelihood of progression to tertiary education. This later-born disadvantage also holds across generations, with the children of those with many older siblings achieving lower levels of educational attainment. Despite these differences, we find that while individual and descendant income is negatively related to the number of siblings, it is not influenced by the relative age of siblings. Thus, our findings imply that the educational disadvantage of later-born children, demonstrated here and in numerous other studies, does not necessarily translate into reduced earnings in adulthood. We discuss potential explanations for this pattern of results, and consider some important directions for future research into sibling configuration and wellbeing in modern societies.

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title: Family Size and Achievement.
abstract: The children born since the end of the postwar baby boom are the first in American history to come primarily from small familiesfamilies of three or fewer children. Judith Blake calls this momentous change the sibsize revolution, and this book focuses on the cognitive and educational consequences to children of families of different sizes."

title: Intelligence Test Scores and Birth Order among Young Norwegian Men (Conscripts) Analyzed within and between Families.
abstract: The present paper reports the results of a within and between family analysis of the relation between birth order and intelligence. The material comprises more than a quarter of a million test scores for intellectual performance of Norwegian male conscripts recorded during 1984–2004. Conscripts, mostly 18–19 years of age, were born to women for whom almost complete reproductive histories were obtained. Women with single births only 1967–1998 and first birth 1967–1976 were selected for analyses. The grand mean stanine score for intellectual performance standardized for age and calendar year was 5.05 (SD = 1.80). The mean standardized score decreased with size of sibship and with higher birth orders in all sibship sizes. These patterns as well as the size of the difference between birth orders 1 and 3 were rather similar between and within families. Among 63 951 adjacent sibling pairs the mean standardized scores were 5.18 (95% confidence interval [CI]: 5.16, 5.19) for the elder and 4.93 (95% CI: 4.91, 4.94) for the younger brother. The difference in mean of standardized scores between adjacent siblings was − 0.251 (95% CI: − 0.270, − 0.231). The difference in mean standardized scores between brothers of adjacent birth orders increased with higher maternal level of education, was highest between brothers of married women, higher with paternal income and decreased with sibship size and longer spacing between births.

title: Birth order matters: the effect of family size and birth order on educational attainment
abstract: Using the British Household Panel Survey, we investigate if family size and birth order affect children’s subsequent educational attainment. Theory suggests a trade-off between child quantity and “quality” and that siblings are unlikely to receive equal shares of parental resources devoted to children’s education. We construct a new birth order index that effectively purges family size from birth order and use this to test if siblings are assigned equal shares in the family’s educational resources. We find that the shares are decreasing with birth order. Ceteris paribus, children from larger families have less education, and the family size effect does not vanish when we control for birth order. These findings are robust to numerous specification checks.

title: Number of siblings and intellectual development. The resource dilution explanation.
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title: Reconsidering the effects of sibling configuration: Recent advances and challenges
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title: Influences on childhood height: comparing two generations in the 1958 British birth cohort.
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The 1958 British birth cohort study includes all children born between March 3, 1958 and March 9, 1958, who were followed to age 41 yr, and one-third of their offspring in 1991. Childhood height in each generation (measured at 7 yr for cohort members and 4-18 yr for offspring) was converted to a standard deviation score based on the 1990 British growth reference. We used multilevel models to analyse influences on height in order to allow for the hierarchical within-family data structure.



Childhood height increased by 1 cm between 1958 cohort members and their offspring. Several influences on childhood height in the older generation (maternal smoking, breastfeeding, maternal age, social class, maternal education, and parental divorce) did not affect childhood height in the younger generation. Parental height was most strongly associated with childhood height and effects did not diminish between generations [adjusted increase approximately 2 cm for 1 maternal or paternal height standard deviation score (SDS)]. Third- or later-borns and those with three or more siblings had deficits of 1-2 cm (adjusted estimates) in both generations. Other factors, particularly indicators of socioeconomic position, showed weaker effects in the younger generation. For example, the growth deficit of 1.1 cm (adjusted estimate) among cohort members from households with >1.5 persons/room had disappeared in the offspring.



Within Great Britain, the adverse effects of environmental factors on childhood height have lessened between recent generations.

title: Childhood circumstances and anthropometry: The Boyd Orr cohort
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title: Birth order progressively affects childhood height
abstract: There is evidence suggesting that first‐born children and adults are anthropometrically different to later‐borns. Thus, we aimed to assess whether birth order was associated with changes in growth and metabolism in childhood.

title: Sibship size and intellectual development: Is the relationship causal?
abstract: In this study we test the alternative interpretation of the effect of sibship size on childs intellectual development through sibling analysis and analysis of repeated measures of the same individuals. Both analyses are variations of change models or fixed-effects models. Change models enable us to control permanent family effects including family socioeconomic status (SES) family genetic makeup and intellectual atmosphere in the home by `differencing them out. Thus we can determine if and how much the sibship-size effect is confounded by other family influences that are difficult or impossible to control in conventional regression analysis. The data are from the [U.S.] National Longitudinal Survey of Youth (NLSY). Also included are comments by Meredith Phillips (pp. 188-92) and D. B. Downey B. Powell L. C. Steelman and S. Pribesh (pp. 193-98) and a reply by Guo and VanWey (pp. 199-206).

title: The Impacts of Family Size on Investment in Child Quality
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title: Trade-offs in modern parenting: a longitudinal study of sibling competition for parental care
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title: WHEN BIGGER IS NOT BETTER: FAMILY SIZE, PARENTAL RESOURCES, AND CHILDREN'S EDUCATIONAL PERFORMANCE*
abstract: Although the inverse relationship between the number of siblings and childrens educational performance has been well established explanations for this relationship remain primitive. One explanation resource dilution posits that parents have finite levels of resources (time energy money etc.) and that these resources are diluted among children as sibship size increases. I provide a more rigorous investigation of the dilution model than previous studies testing its implications with a sample of 24599 eighth graders from the 1988 [U.S.] National Education Longitudinal Study. My analyses support the resource dilution model in three ways. First the availability of parental resources decreases as the number of siblings increases net of controls....Second parental resources explain most or all of the inverse relationship between sibship size and educational outcomes. Finally interactions between sibship size and parental resources support the dilution model as children benefit less from certain parental resources when they have many versus few siblings.

title: ALLOCATION OF TIME TO PRESCHOOL CHILDREN AND EDUCATIONAL OPPORTUNITY
abstract: Using a unique data source on family time use both in and outside the home, we obtained estimates of parental time allocated to preschool children for several socioeconomic status groups. We find that while high status mothers have a relatively high potential wage, they spend from two to three times as much time in preschool child care as do low status mothers. To the extent that this class differential in time investments to preschool children influences cognitive achievement, our results indicate again that equal educational programs across different school systems need not imply equal educational opportunity.

title: Parental Care of Children: Time Diary Estimates of Quantity, Predictability, and Variety
abstract: Time inputs to children are measured using data from the recent Time Use Survey conducted by the University of Michigan. We analyze time parents devote to their children, particularly in their preschool years, in an attempt to find out if there are social-class and education-of-wife differentials in this particular time use that may provide some insight into the intergenerational transmission of income inequality. We also offer some comment on labor supply of women and child care by men. We find that more-educated women spend more time playing with children, helping with the teaching of children, and in child-related travel.

title: Optimizing Modern Family Size
abstract: Modern industrialized populations lack the strong positive correlations between wealth and reproductive success that characterize most traditional societies. While modernization has brought about substantial increases in personal wealth, fertility in many developed countries has plummeted to the lowest levels in recorded human history. These phenomena contradict evolutionary and economic models of the family that assume increasing wealth reduces resource competition between offspring, favoring high fertility norms. Here, we review the hypothesis that cultural modernization may in fact establish unusually intense reproductive trade-offs in wealthy relative to impoverished strata, favoring low fertility. We test this premise with British longitudinal data (the Avon Longitudinal Study of Parents and Children), exploring maternal self-perceptions of economic hardship in relation to increasing family size and actual socioeconomic status. Low-income and low-education-level mothers perceived the greatest economic costs associated with raising two versus one offspring. However, for all further increases to family size, reproduction appears most expensive for relatively wealthy and well-educated mothers. We discuss our results and review current literature on the long-term consequences of resource dilution in modern families.

title: Parental investment and the optimization of human family size
abstract: Human reproductive behaviour is marked by exceptional variation at the population and individual level. Human behavioural ecologists propose adaptive hypotheses to explain this variation as shifting phenotypic optima in relation to local socioecological niches. Here we review evidence that variation in fertility (offspring number), in both traditional and modern industrialized populations, represents optimization of the life-history trade-off between reproductive rate and parental investment. While a reliance on correlational methods suggests the true costs of sibling resource competition are often poorly estimated, a range of anthropological and demographic studies confirm that parents balance family size against offspring success. Evidence of optimization is less forthcoming. Declines in fertility associated with modernization are particularly difficult to reconcile with adaptive models, because fertility limitation fails to enhance offspring reproductive success. Yet, considering alternative measures, we show that modern low fertility confers many advantages on offspring, which are probably transmitted to future generations. Evidence from populations that have undergone or initiated demographic transition indicate that these rewards to fertility limitation fall selectively on relatively wealthy individuals. The adaptive significance of modern reproductive behaviour remains difficult to evaluate, but may be best understood in response to rising investment costs of rearing socially and economically competitive offspring.

title: Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society
abstract: Adaptive accounts of modern low human fertility argue that small family size maximizes the inheritance of socioeconomic resources across generations and may consequently increase long-term fitness. This study explores the long-term impacts of fertility and socioeconomic position (SEP) on multiple dimensions of descendant success in a unique Swedish cohort of 14 000 individuals born during 1915–1929. We show that low fertility and high SEP predict increased descendant socioeconomic success across four generations. Furthermore, these effects are multiplicative, with the greatest benefits of low fertility observed when SEP is high. Low fertility and high SEP do not, however, predict increased descendant reproductive success. Our results are therefore consistent with the idea that modern fertility limitation represents a strategic response to the local costs of rearing socioeconomically competitive offspring, but contradict adaptive models suggesting that it maximizes long-term fitness. This indicates a conflict in modern societies between behaviours promoting socioeconomic versus biological success. This study also makes a methodological contribution, demonstrating that the number of offspring strongly predicts long-term fitness and thereby validating use of fertility data to estimate current selective pressures in modern populations. Finally, our findings highlight that differences in fertility and SEP can have important long-term effects on the persistence of social inequalities across generations.

title: Biased parental investment and reproductive success in Gabbra pastoralists
abstract: Demographic data from 848 Gabbra households are used to examine the relationships between herd size and reproductive success in relation to sex, in a traditional, pastoralist population. The number of camels in the household herd has a significant positive effect on the reproductive success of both men and women, although the effect of wealth is greater for men, as predicted from evolutionary theory. The greater the number of elder brothers a man has, the lower his reproductive success, as a result of a smaller initial herd and a later age at marriage. This is not true for women –number of elder sisters does not have a measurable effect on a woman’s fertility, although it does have a small, negative effect on the size of her dowry. These results are interpreted as competition between same-sex siblings for parental investment, in the form of their father’s herd, which is more intense between sons than daughters as parental investments are greatest in males.

title: Intrafamilial resource competition and mate competition shaped social‐group‐specific natal dispersal in the 18th and 19th century Krummhörn population
abstract: We describe the natal dispersal patterns of the Krummhörn population as the outcome of intrafamilial competition. Depending on the affiliation with a specific social group and the sex of the individual, this competition is driven by different factors and obeys a different functional logic: The dispersal patterns of the daughters of landless workers allow a mate competition scenario to be detected, whereas the dispersal behavior of the children of farmers (especially of the sons) is driven by a resource competition scenario.  2008.

title: Birth interval and the sex of children in a traditional African population: an evolutionary analysis.
abstract: Birth interval is a major determinant of rates of fertility, and is also a measure of parental investment in a child. In this paper the length of the birth interval in a traditional African population is analysed by sex of children. Birth intervals after the birth of a boy were significantly longer than after the birth of a girl, indicating higher parental investment in boys. However, in women of high parity, this differential disappeared. Birth intervals for women with no son were shorter than for those with at least one son. All these results are compatible with an evolutionary analysis of reproductive decision-making. First born sons have particularly high reproductive success, daughters have average reproductive success and late born sons have low reproductive success. The birth interval follows a similar trend, suggesting that longer birth intervals represent higher maternal investment in children of high reproductive potential.

title: Sex-biased lactational duration in a human population and its reproductive costs
abstract: SummaryWe tested the proposition that among humans (1) differences in lactational duration result in differences in costs of reproduction even under rich nutritional conditions; and (2) elimination of factors postulated to favor male-biased parental care will be reflected in elimination or reversal of sex-biased care. To do so, we examined the relationship between lactational duration and fertility among Hutterites, a communal-living human population in which the levels of nutritional resources and fertility are high, breast-feeding is the norm, contraceptive use is limited and the collective social and economic system results in low resource variance among individuals. We demonstrate that even under good nutritional conditions, duration of nursing was a significant predictor of the length of time to next pregnancy and that nursing continued to suppress fertility after the resumption of menses. Moreover, we find that daughters were nursed longer than sons, leading to a longer interval to next pregnancy. We examine this uncommon, but not unique, finding of female-biased human parental care in the light of Hutterite social structure, and we explore the consistency of this finding with the most applicable models of parental investment.

title: Sons, Daughters, and Parental Behaviour
abstract: The prevalence of son preference and its implications for family behaviour in developing countries have received a great deal of scholarly attention, but child-gender bias is believed to be empirically unimportant in wealthy, non-traditional societies. Studies by sociologists and psychologists during the past 30 years, however, have documented consistent discrepancies between the behaviour of parents of sons and parents of daughters--boys tend to increase marital stability and marital satisfaction relative to girls, and fathers spend more time with, and are more involved with, sons than daughters. In recent years, economists have begun to contribute to the child-gender literature, re-examining the effects of sons and daughters on family structure and parental involvement with larger samples and greater concern for possible sources of selection bias. Other economic outcomes, such as market work and earnings, have also been studied, and some investigators have exploited the randomness of child gender as a source of exogenous variation in parental behaviour. In general, recent results suggest that child gender does affect family stability and the time allocation of parents, but it is not clear whether these responses reflect parental preferences for boys rather than girls or differences in the constraints parents face.

title: The Demand for Sons
abstract: Do parents have preferences over the gender of their children, and if so, does this have negative consequences for daughters versus sons? In this paper, we show that child gender affects the marital status, family structure, and fertility of a significant number of American families. Overall, a first-born daughter is significantly less likely to be living with her father compared to a first-born son. Three factors are important in explaining this gap. First, women with first-born daughters are less likely to marry. Strikingly, we also find evidence that the gender of a child in utero affects shotgun marriages. Among women who have taken an ultrasound test during pregnancy, mothers who have a girl are less likely to be married at delivery than those who have a boy. Second, parents who have first-born girls are significantly more likely to be divorced. Third, after a divorce, fathers are much more likely to obtain custody of sons compared to daughters. These three factors have serious negative income and educational consequences for affected children. What explains these findings? In the last part of the paper, we turn to the relationship between child gender and fertility to help sort out parental gender bias from competing explanations for our findings. We show that the number of children is significantly higher in families with a first-born girl. Our estimates indicate that first-born daughters caused approximately 5500 more births per year, for a total of 220,000 more births over the past 40 years. Taken individually, each piece of empirical evidence is not sufficient to establish the existence of parental gender bias. But taken together, the weight of the evidence supports the notion that parents in the U.S. favour boys over girls.

title: Sons, Daughters, and the Risk of Marital Disruption
abstract: The association between the sex of children and their parents' risk of marital disruption is examined using the June 1980 Current Population Survey. The finding is that sons reduce the risk of marital disruption by 9% more than do daughters. This difference holds across marriage cohorts, racial groups, and categories of mother's education. A compelling explanation for these findings, supported by data from the National Survey of Children, stresses a father's greater role in raising sons than daughters and his consequently greater involvement in the family. Children provide a new basis for marital cohesion, one that rests on attachments and obligations to children. For fathers, the obligations and attachments are greater if they have sons.

title: The Effects of Sons and Daughters on Men's Labor Supply and Wages
abstract: In this paper, we estimate the effects of children and the differential effects of sons and daughters on men's labor supply and hourly wage rates. The responses to fatherhood of two cohorts of men from the PSID sample are examined separately, and we use fixed-effects estimation to control for unobserved heterogeneity. We find that fatherhood significantly increases the hourly wage rates and annual hours of work for men from both cohorts. Most notably, men's labor supply and wage rates increase more in response to the births of sons than to the births of daughters.

title: Gendering family composition: Sex preferences for children and childbearing behavior in the Nordic countries
abstract: It has been argued that a society’s gender system may influence parents’ sex preferences for children. If this is true, one should expect to find no evidence of such preferences in countries with a high level of gender equality. In this article, we exploit data from population registers from Denmark, Finland, Norway, and Sweden to examine continuities and changes in parental sex preferences in the Nordic countries during the past three to four decades. First, we do not observe an effect of the sex of the firstborn child on second-birth risks. Second, we detect a distinct preference for at least one child of each sex among parents of two children. For third births, Danish, Norwegian, and Swedish parents seem to develop a preference for having a daughter, while Finns exhibit a signifiant preference for having a son. These findings show that modernization and more equal opportunities for women and men do not necessarily lead to parental gender indifference. On the contrary, they may even result in new sex preferences.

title: Parental Status and Differential Investment in Sons and Daughters: Trivers-Willard Revisited
abstract: According to the Trivers-Willard (T-W) hypothesis there is an interaction between individual status and investment in offspring such that high-status individuals invest more in boys, and low-status individuals invest more in girls. Parental investment may be both physiological and affect the sex ratio of offspring, or it may be psychological and affect resource allocation to offspring. I test both components of the hypothesis using cumulative U.S. General Social Survey (GSS) data and find results that support T-W. Using years of education attained as an indirect measure of parental investment, I find that sons of high-status fathers attain more education than daughters and that the daughters of low-status fathers attain more education than sons. Supporting the sex ratio component of T-W, I find that high-status men have more sons.

title: The Liability of Having Brothers: Paying for College and the Sex Composition of the Family.
abstract: Although sibship size has become a standard measure in the study of academic achievement and attainment, logical and theoretically meaningful extensions of this variable often have been ignored. Sex composition-the number of brothers and the number of sisters-is one such extension. This article reports on a study of the impact of sex composition on strategies for funding a college education. Data on 454 seniors at two large universities confirm that the number of brothers poses a greater obstacle than does the number of sisters to parents' financial support of their children's college education. In addition, the alternative means by which students fund their college education are more strongly affected by the number of brothers than by the number of sisters they have. The authors conclude that sex composition of sibship strongly merits inclusion in educational research.

title: Parent-Child Quality Time: Does Birth Order Matter?
abstract: Using data from the American Time Use Survey, I find that a first-born child receives 20-30 more minutes of quality time each day with his or her parent than a second-born child of the same age from a similar family. The birth-order difference results from parents giving roughly equal time to each child at any point in time while the amount of parent-child quality time decreases as children get older. These results provide a plausible explanation for recent research showing a very significant effect of birth order on child outcomes.

title: Parental investment: how an equity motive can produce inequality.
abstract: The equity heuristic is a decision rule specifying that parents should attempt to subdivide resources more or less equally among their children. This investment rule coincides with the prescription from optimality models in economics and biology in cases in which expected future return for each offspring is equal. In this article, the authors present a counterintuitive implication of the equity heuristic: Whereas an equity motive produces a fair distribution at any given point in time, it yields a cumulative distribution of investments that is unequal. The authors test this analytical observation against evidence reported in studies exploring parental investment and show how the equity heuristic can provide an explanation of why the literature reports a diversity of birth order effects with respect to parental resource allocation.

title: Growth in academic achievement and teaching younger siblings
abstract: A longitudinal follow-up od Smith's (1990) study of associations between academic achievement and self-reported teaching of younger siblings uses the data set on which the previous research was based, plus results of academic achievement tests from two years later for 566 members of Smith's original sample. Instead of the nonlinear associations between teaching younger siblings and reading and language achievement reported in the previous study, this analysis reveals positive linear associations between growth in academic achievement over the two-year period and the measure of teaching younger siblings

title: Explaining the Relation Between Birth Order and Intelligence
abstract: Negative associations between birth order and intelligence level have been found in numerous studies. The explanation for this relation is not clear, and several hypotheses have been suggested. One family of hypotheses suggests that the relation is due to more-favorable family interaction and stimulation of low-birth-order children, whereas others claim that the effect is caused by prenatal gestational factors. We show that intelligence quotient (IQ) score levels among nearly 250,000 military conscripts were dependent on social rank in the family and not on birth order as such, providing support for a family interaction explanation.

title: Siblings and childhood mental health: evidence for a later-born advantage.
abstract: The social and health sciences have often emphasised the negative impacts of large sibship size and late birth order on childhood. For example, it is now well established that, other things being equal, children in large families and/or with many older siblings, receive lower allocations of care time from both parents, are more likely to grow up in conditions of economic hardship, and, as a likely consequence, exhibit relatively poor educational and physical health outcomes. Few researchers have, however, quantitatively assessed how siblings may influence indicators of mental health, where it is conceivable that social interactions with siblings may have a positive influence. Here, using data from a large British cohort survey (the Avon Longitudinal Study of Parents and Children), we explored the effects of sibling configuration on the Strengths and Difficulties Questionnaire, as a multidimensional index for mental health problems. We demonstrate a significant socio-economic gradient in mental health between the ages of three and nine years, but little evidence for negative effects of large sibship size. Rerunning this analysis to examine birth order, a much clearer pattern emerged; the presence of older siblings was associated with relatively good mental health, while the presence of younger siblings was associated with relatively poor mental health. This suggests that being born into a large family, providing the child is not joined by subsequent siblings, may carry important benefits unconsidered by past research. We discuss possible interpretations of this pattern and the wider implications for understanding the family context of child development.

title: Time trends in adolescent mental health.
abstract: Existing evidence points to a substantial rise in psychosocial disorders affecting young people over the past 50 years (Rutter & Smith, 1995). However, there are major methodological challenges in providing conclusive answers about secular changes in disorder. Comparisons of rates of disorder at different time points are often affected by changes in diagnostic criteria, differences in assessment methods, and changes in official reporting practices. Few studies have examined this issue using the same instruments at each time point.



The current study assessed the extent to which conduct, hyperactive and emotional problems have become more common over a 25-year period in three general population samples of UK adolescents. The samples used in this study were the adolescent sweeps of the National Child Development Study and the 1970 Birth Cohort Study, and the 1999 British Child and Adolescent Mental Health Survey. Comparable questionnaires were completed by parents of 15-16-year-olds at each time point (1974, 1986, and 1999).



Results showed a substantial increase in adolescent conduct problems over the 25-year study period that has affected males and females, all social classes and all family types. There was also evidence for a recent rise in emotional problems, but mixed evidence in relation to rates of hyperactive behaviour. Further analyses using longitudinal data from the first two cohorts showed that long-term outcomes for adolescents with conduct problems were closely similar. This provided evidence that observed trends were unaffected by possible changes in reporting thresholds.

title: Social and biological determinants of reproductive success in Swedish males and females born 1915–1929
abstract: To investigate whether early life characteristics predict subsequent reproductive success in a post-demographic transition population; to ascertain the pathways mediating any observed effects; and to examine whether any of the above effects are gender-specific.

Multi-generational data from a representative, population-based birth cohort and using linkage to routinely collected data.

Uppsala, Sweden.

13 666 individuals born in Uppsala university hospital between 1915 and 1929, who were traced and linked to all registered descendants up to 2002.

Birthweight for …

title: 027 Birth characteristics and early-life social characteristics predict unequal educational outcomes: consistency across Swedish cohorts born 1915–1929 and 1973–1980
abstract: To investigate early-life biological and social predictors of educational outcomes, and compare the nature and magnitude of these effects across twentieth century Sweden.  Multi-generational data from a representative, population-based birth cohort, with linkage to routinely collected data.  Swedish male and females born 1915–1929 and 9465 of their grandchildren born 1973-1980, restricting participants to those who remained alive and in Sweden until age 20. Characteristics measured at birth Sex, birthweight for gestational age, preterm birth, birth multiplicity, birth order, mother's age, mother's marital status and family social class. Educational outcomes School achievement was measured using standardised schoolmarks in elementary school. Education continuation was measured as a) senior school attendance and b) entrance to higher education.  The predictors of both school achievement and education continuation were very similar in the two cohorts, and effect sizes were usually at least as large in the younger cohort. In both cohorts, the independent predictors of better schoolmarks were: female gender (adjusted effect size 0.35 standard deviations (SD) in 1915–1929, 0.41SD in 1979-1980); higher birthweight for gestational age (0.09SD in 1915–1929, 0.23SD in 1979–1980 for highest vs lowest quintile); lower birth order (eg, 0.33SD in 1915–1925, 0.65SD in 1973–1980 for birth order 1 vs 4–5); older mother (eg, 0.12SD in 1915–1929, 0.34SD in 1973–1980 for 35–39 years vs 20–24 years); married mother (0.14SD in 1915–1929, 0.15SD in 1973–1980 for married vs unmarried); and higher family social class (eg, 0.39SD in 1915–1929, 0.66SD in 1973–1980 for high/mediate non-manual vs semi/unskilled manual). There were no independent effects of preterm or twin status. The same characteristics predicted education continuation, except that for this outcome the older cohort now showed a marked male advantage and no birthweight effect. Even after adjusting for school achievement, education continuation was still predicted by lower birth order, older mother, married mother and higher social class.  Multiple early-life characteristics predicted educational outcomes across the lifecourse. These included size at birth (foetal growth rate) and family composition effects which typically receive far less attention than socio-economic influences. A range of pathways including impaired cognitive development, are likely to mediate these effects. Most effects were remarkably stable across the half-century separating our cohorts, indicating their potential relevance for understanding educational inequalities in populations around the world. Greater understanding of educational inequalities would, in turn, shed light onto a major mechanism whereby health inequalities are created and recreated across generations.

title: A simple method for converting an odds ratio to effect size for use in meta-analysis.
abstract: A systematic review may encompass both odds ratios and mean differences in continuous outcomes. A separate meta-analysis of each type of outcome results in loss of information and may be misleading. It is shown that a ln(odds ratio) can be converted to effect size by dividing by 1.81. The validity of effect size, the estimate of interest divided by the residual standard deviation, depends on comparable variation across studies. If researchers routinely report residual standard deviation, any subsequent review can combine both odds ratios and effect sizes in a single meta-analysis when this is justified.

title: Multiple Imputation of Missing Values: Update
abstract: This article describes a substantial update to mvis, which brings it more closely in line with the feature set of S. van Buuren and C. G. M. Oudshoorn's implementation of the MICE system in R and S-PLUS (for details, see http://www.multiple-imputation.com). To make a clear distinction from mvis, the principal program of the new Stata release is called ice. I will give details of how to use the new features and a practical illustrative example using real data. All the facilities of mvis are retained by ice. Some improvements to micombine for computing estimates from multiply imputed datasets are also described.

title: Are sibling relationships protective? A longitudinal study.
abstract: Although the protective effects of familial and parental support have been studied extensively in the child psychopathology literature, few studies have explored the protective quality of positive sibling relationships.



A two-wave longitudinal design was used to examine the protective effect of positive sibling relationships on child adjustment for children experiencing stressful life events. Mothers reported on stressful life events and child adjustment. Older siblings assessed the quality of relationship between themselves and target children.



Sibling affection moderated the relationship between stressful life events and internalizing symptomatology but not the relationship between stressful life events and externalizing symptomatology. Notably, the protective effect of sibling affection was evident regardless of mother-child relationship quality.



Positive sibling relationships are an important source of support for children experiencing stressful life events. Implications for intervention are discussed.

title: Playing Well with Others in Kindergarten: The Benefit of Siblings at Home
abstract: There are many reasons to expect that children gain something by growing up with siblings, yet there is surprisingly scant evidence of this advantage. Indeed, the vast majority of research assessing the consequences of siblings reports negative effects: Children with many siblings do not perform as well in school as children with few siblings. By focusing almost exclusively on educational outcomes, however, previous studies have neglected ways in which children might benefit from siblings. One possibility, for example, is that siblings promote children's social and interpersonal skills. In this study, we analyze a sample of kindergartners (N = 20,649) from The Early Childhood Longitudinal Study—Kindergarten Class of 1998–99 to replicate the often-noted negative relationship between number of siblings and cognitive outcomes, and then demonstrate that this pattern does not extend to social skills. Findings are consistent with the view that children negotiate peer relationships better when they grow up with at least one sibling.

title: Number of Siblings and Friendship Nominations Among Adolescents
abstract: Considerable social science research questions the benefit of siblings. The most prominent example is the consistent negative association between sibship size and educational outcomes. But more recent work among kindergartners uncovered a potentially positive outcome—greater social skills—at least for those who have at least one sibling. We extend this line of inquiry to adolescence to see if there are long-term negative consequences of growing up without any siblings. Analyzing 13,466 youths from the National Longitudinal Study of Adolescent Health, we find no evidence that only children receive fewer peer nominations of friendship than youths with one (or more than one) sibling(s). Our results suggest that the previously observed social skills deficit among only children in kindergarten appears to be overcome by adolescence.

title: Sibship Sex Composition: Effects on Educational Attainment
abstract: This study decomposes the detrimental effects of increased sibship on educational attainment by the sex of the respondent and his/her siblings. Previous theories regarding the interaction of gender and sibship sex composition are reviewed and a new hypothesis is offered: a revision of the sex minority hypothesis, positing that an increased number of siblings of the opposite sex (regardless of the of the respondent's gender) are harmful to educational achievement since sex minority children may find their gender-specific needs unmet, may suffer from socialization by the family that conflicts with sex role expectations within the educational system, or because there may exist returns to scale for “gender-specific”goods within the household. Findings reveal that it is the number of opposite sex siblings that most hurts educational attainment efforts, marshalling support for the revised sex minority hypothesis.