Research keywords

Timing of first birth, seasonal variation in births, Intergenerational influences on fertility, effects of education and social background on fertility, effects of life experiences on fertility, effects of networks of social relations on fertility

Publications:

Jalovaara, M., Neyer, G., Andersson, G., Dahlberg, J., Dommermuth, L., Fallesen, P., & Lappegård, T. (2019). Education, gender, and cohort fertility in the Nordic countries. European Journal of Population, 1-24.

Dahlberg, J., & Kolk, M. (2018). Explaining Swedish sibling similarity in fertility: Parental fertility behavior vs. social background. Demographic Research, 39, 883-896.

Dahlberg, J., & Andersson, G. (2018). Changing seasonal variation in births by sociodemographic factors: a population-based register study. Human Reproduction Open, 2018(4), hoy015.

Miranda, V., Dahlberg, J., and Andersson, G. (2018) Parents’ Preferences for Sex of Children in Sweden: Attitudes and Outcomes. Popul Res Policy Rev. Advance online publication. doi: 10.1007/s11113-018-9462-8

Dahlberg, J. (2018). Death Is Not the End: A Register-Based Study of the Effect of Parental Death on Adult Children’s Childbearing Behavior in Sweden. OMEGA-Journal of Death and Dying. Advance online publication. doi: 10.1177/0030222818756740

Dahlberg, J. (2015). Social Background and Becoming a Parent in Sweden: A Register-Based Study of the Effect of Social Background on Childbearing in Sweden. European Journal of Population, 31(4), 417-444. 

Elvander, C., Dahlberg, J., Andersson, G. and Cnattingius, S. (2015). Mode of delivery and the probability of subsequent childbearing: a popula-tion-based register study. BJOG: An International Journal of Obstet-rics and Gynaecology, 122(12), 1593-1600.

Dahlberg, J. (2013). Family Influence in Fertility: A Longitudinal Analysis of Sibling Correlations in First Birth Risk and Completed Fertility among Swedish men and women. Demographic Research, 29, 233-246.

Doctoral thesis:

Dahlberg Johan (2016 ) Parents, Children and Childbearing.

A selection from Stockholm University publication database

• Educational Differences in Cohort Fertility Across Sub-national Regions in Europe

  2021. Jessica Nisén (et al.). European Journal of Population 37, 263-295

  Article

  Educational differences in female cohort fertility vary strongly across high-income countries and over time, but knowledge about how educational fertility differentials play out at the sub-national regional level is limited. Examining these sub-national regional patterns might improve our understanding of national patterns, as regionally varying contextual conditions may affect fertility. This study provides for the first time for a large number of European countries a comprehensive account of educational differences in the cohort fertility rate (CFR) at the sub-national regional level. We harmonise data from population registers, censuses, and large-sample surveys for 15 countries to measure women's completed fertility by educational level and region of residence at the end of the reproductive lifespan. In order to explore associations between educational differences in CFRs and levels of economic development, we link our data to regional GDP per capita. Empirical Bayesian estimation is used to reduce uncertainty in the regional fertility estimates. We document an overall negative gradient between the CFR and level of education, and notable regional variation in the gradient. The steepness of the gradient is inversely related to the economic development level. It is steepest in the least developed regions and close to zero in the most developed regions. This tendency is observed within countries as well as across all regions of all countries. Our findings underline the variability of educational gradients in women's fertility, suggest that higher levels of development may be associated with less negative gradients, and call for more in-depth sub-national-level fertility analyses by education.

  Read more about Educational Differences in Cohort Fertility Across Sub-national Regions in Europe

• Fecundity and human birth seasonality in Sweden

  2019. Johan Dahlberg, Gunnar Andersson. Reproductive Health 16

  Article

  Background: It is well-established that couples' fecundities vary widely. Each couple has a relatively constant monthly probability of conceiving, which can vary from zero to quite high. This underlying probability is usually expressed as the time (number of menstrual cycles) the couple requires to conceive. Couples with high fecundity will, on average, need fewer cycles than couples with low fecundity. It is also well-documented that almost all human populations exhibit seasonal variation in births. Most European countries show seasonal variation that usually peak in the spring and are the lowest during the last quarter of the year. The increasingly strong pattern of depressed birth rates in November and December is likely explained by the December-January cut-off threshold for Swedish pupils' school entry and their parents increasing awareness of the negative effects on school outcomes for children who are juniors in the school-entry cohort they belong to. To actively plan births for a specific time of the year, couples need to have some knowledge of the time required for them to conceive.

  Methods: We use the duration between marriage of childless couples and first birth as a proxy measure of couples' fecundity. Based on this time-to-pregnancy measure we study to what extent couples' capacity to conceive affects the seasonality of their second births. We hypothesize that in a society with highly controlled fertility and a strong norm of having at least two children, sub-fertile couples will on average show less seasonal variation in second births. Sub-fertile couples, requiring more time to conceive the first time, will be less likely to try to target a desired birth month for their second child because doing so could jeopardize fulfilling their desired family size. We apply multinomial logistic regressions on 81,998 Swedish couples who married while being childless and subsequently gave birth to at least two children between 1990 and 2012, to investigate fecundity's role in seasonal variation in second births.

  Results: We found that seasonal variation in second births was strongly associated with couples' observed fecundity, measured as the duration between marriage formation and first birth. Our results support the hypothesis that sub-fertile couples, requiring more time to conceive the first time, show less seasonal variation in second births. The seasonal variations in second order births among couples with normal fecundity shows some similarities to traditional patterns as seen in agricultural and industrial societies of the past, with high numbers of births during the spring, and low numbers during the last quarter of the year. However, two important differences are notable. The characteristic Christmas peak in September has vanished, and the low birth rates in November and December come out much stronger than in the past.

  Conclusions: The birth seasonality among couples with normal fecundity are what we would expect if couples actively plan their births according to the cut-off date for Swedish pupils' school entry. We argue that our findings support the notion that scheduled childbirth is a reality in contemporary sociality.

  Read more about Fecundity and human birth seasonality in Sweden

• Education, Gender, and Cohort Fertility in the Nordic Countries

  2019. Marika Jalovaara (et al.). European Journal of Population 35 (3), 563-586

  Article

  Systematic comparisons of fertility developments based on education, gender and country context are rare. Using harmonized register data, we compare cohort total fertility and ultimate childlessness by gender and educational attainment for cohorts born beginning in 1940 in four Nordic countries. Cohort fertility (CTF) initially declined in all four countries, although for cohorts born in the 1950s and later, the CTF remained stable or declined only modestly. Childlessness, which had been increasing, has plateaued in Denmark, Norway and Sweden. Women’s negative educational gradient in relation to total fertility has vanished, except in Finland, while men’s positive gradient has persisted. The highest level of men’s childlessness appears among the least educated. In the oldest female cohorts, childlessness was highest among the highly educated, but these patterns have changed over the cohorts as childlessness has increased among the low educated and remained relatively stable among higher educated women. In Denmark, Norway and Sweden, childlessness is now highest among the least educated women. We witness both a new gender similarity and persistent (among men) and new (among women) educational disparities in childbearing outcomes in the Nordic region. Overall, the number of low educated has decreased remarkably over time. These population segments face increasing social and economic disadvantages that are reflected as well in their patterns of family formation.

  Read more about Education, Gender, and Cohort Fertility in the Nordic Countries

• Changing seasonal variation in births by sociodemographic factors

  2018. Johan Dahlberg, Gunnar Andersson. Human Reproduction Open (4)

  Article

  STUDY QUESTION: Have seasonal variations in births by factors related to maternal education, age, parity and re-partnering changedover a 72-year period? SUMMARY ANSWER: Seasonal variation in births has been reduced overall but also changed its pattern over the last seven decades. WHAT IS KNOWN ALREADY: The number of births varies markedly by season, but the causes of this variation are not fully understood.Seasonality of births is, in some populations, strongly influenced by sociodemographic factors. STUDY DESIGN SIZE, DURATION: A longitudinal study design was used by analysing the seasonal variation in live births between 1940and 2012, and relating it to mothers’ sociodemographic characteristics at the time of childbirth (maternal education, age, parity and repartnering). PARTICIPANTS/MATERIALS, SETTING, METHODS: Register data on 6 768 810 live births in Sweden between 1940 and 2012were used. Information on biological parents are available for more than 95% of all births. Multinomial logistic regressions were used to calculatepredicted probabilities of giving birth for each calendar month. MAIN RESULTS AND THE ROLE OF CHANCE: Between 1940 and 1999, Swedish birth rates showed the typical seasonal variationwith high numbers of births during the spring, and low numbers of births during the last quarter of the year. However, during the 21st century,the seasonal variation in fertility declined so that only minor variation in birth rates between February and September now remains. Still, thepattern of low birth rates at the end of the year remains and has even become more pronounced from the 1980s onwards. The characteristic‘Christmas effect’ that used to be visible in September has vanished over the last 30 years. The roles in seasonal variation of maternal education,the mother’s age, parity and instances where the mother has re-partnered between subsequent births changed during the second half ofthe 20th century. From 1980s onwards, the decline in birth rates during the last quarter of the year became particularly pronounced amonghighly educated mothers. Over the 72 years studied, the seasonal variation among first-time mothers declined steadily and has almost disappearedat the end of the study period. Using data that cover ~180 000 births in each month, all meaningful results are statistically significant. LIMITATIONS REASONS FOR CAUTION: The study uses data from one Nordic country only, making it difficult to draw conclusionsthat may hold for other countries. WIDER IMPLICATIONS OF THE FINDINGS: The typical seasonal variation reported for Sweden between 1940 and 1999, with highnumbers of births during the spring and low numbers of births during the last quarter of the year, is in line with results from most otherEuropean countries during the same time period. However, the significant decline in seasonal variation in the early 21st century is a noveldevelopment. The study underlines that in a society with low fertility and efficient birth control, active choices and behaviours associated withan individual’s sociodemographic characteristics tend to matter more for the seasonal timing of childbearing than environmental factorsrelated to the physiological ability to reproduce and cultural–behavioural factors related to the frequency of intercourse.

  Read more about Changing seasonal variation in births by sociodemographic factors

• Explaining Swedish sibling similarity in fertility

  2018. Johan Dahlberg, Martin Kolk. Demographic Research 39, 883-896

  Article

  Objective: The aim of this descriptive study is to determine which of the family-specific factors, parental fertility behavior or social background, matters most for the intergenerational transmission of fertility.

  Methods: Brother and sister correlations in age at first birth and final family size were estimated using multilevel linear regression on data covering 242,976 Swedish men and women born between 1958 and 1967. To explore how much of siblings’ similarity in fertility can be explained by parental fertility behavior (age at parenthood and number of children) and social background, we analyzed the decrease in sibling correlation when these family-specific factors were added to the unconditional models.

  Results: We found that most of siblings’ similarity in fertility could not be explained by parental fertility behavior and social background, but that they explained a substantive part of siblings’ similarities in age at first birth and a smaller but non-negligible part of siblings’ similarities in completed fertility. Parental fertility behavior and social background explain as much (about 36%) of brothers’ and sisters’ similarities in age at first birth. Parental fertility behavior matters more than social background for sisters’ similarities in completed family size. Parental fertility behavior and social background explain about the same (5%) for brothers’ similarities in completed family size.

  Contribution: This study contributes to the existing understanding of intergenerational transmission of fertility; both methodologically, by introducing a new method to estimate the impact of specific factors shared by siblings, and by determining how much of siblings’ resemblance in fertility can be explained by parental fertility behavior and social background.

  Read more about Explaining Swedish sibling similarity in fertility

• Parents' Preferences for Sex of Children in Sweden

  2018. Vitor Miranda, Johan Dahlberg, Gunnar Andersson. Population 37 (3), 443-459

  Article

  It has been argued that preferences for the sex of children would be small or nonaEuroexisting in relatively gender equal societies. However, previous studies have suggested that a stronger preference for having daughter exists in Scandinavian countries, which are frequently noted for being among the most gender equal societies in the world. Combining new register data on birth rates by sex of the previous children and recent survey data on couples' stated preferences for the sex of children, we show that the preference for daughters has increased in Sweden over the last decade. In addition to the stronger preference for having daughters among twoaEurochild mothers documented in previous research, our findings show that during the previous decade this preference was noticeable also among oneaEurochild parents. Despite Swedish society being known for holding gender equal social norms, interviewed parents openly expressed some degree of preference for having daughters over sons.

  Read more about Parents' Preferences for Sex of Children in Sweden

• Death Is Not the End

  2020. Johan Dahlberg. Omega 81 (1), 80-106

  Article

  Macro-level studies have shown that rapid increases in mortality can affect fertility rates. Parental death has also been linked to negative psychological and physical outcomes, reduced relationship quality, and making bereaved children attach more importance to their families. No prior study has examined whether parental death influences adult children’s fertility at the microlevel. This study applies event history techniques to Swedish multigeneration registers listing 1.5 million individuals with micro data on mortality and fertility to investigate short-term (first birth risk) and long-term (childlessness at age 45) effects of parental death on adult children’s fertility. The principal finding is that parental death during reproductive age affects children’s fertility and this effect is mainly short term. The effects differ to some degree between men and women and depend on the stage of the life course in which the bereavement occurs. Younger individuals experiencing a parental death have a significantly higher first birth risk after the parental death compared with peers who did not experience a parental death. Individuals older than 23 who experience a parental death have no or lower first birth risk after the parental death compared with baseline. Men, compared with women, are more likely to end childless if they experience a parental death.

  Read more about Death Is Not the End

• Parents, Children and Childbearing

  2016. Johan Dahlberg.

  Thesis (Doc)

  This doctoral thesis provides a set of studies of social influences on fertility timing. Swedish register data are used to link individuals to their parents and siblings, thereby allowing the study of impacts of family of origin, social background, and parental death on fertility. The Swedish Medical Birth Register is used to investigate the effect of mode of delivery on higher order births. The thesis consists of an introductory chapter with an overview of the consequences and predictors of the timing of childbearing, and a theoretical framework to explain these relationships. This chapter also includes a section where the contribution to existing knowledge, the relation of the findings to life course theory, and suggestion for further research are discussed. This chapter is followed by four original empirical studies. The first study applies sister and brother correlations to investigate and estimate the impact of family of origin on fertility. It shows that family of origin matters for fertility timing and final family size. The study also shows that the overall importance of family of origin has not changed over the approximately twenty birth cohorts that were studied. The second study introduces three dimensions of social background - occupational class, status, and education - into fertility research. It suggests that social background, independent of individuals’ own characteristics, matters for the timing of first birth and the risk of childlessness. The study also shows that different dimensions of social background should not be used interchangeably. The third study uses the Swedish Medical Birth Register to investigate the effect of mode of delivery on the propensity and birth interval of subsequent childbearing. It demonstrates that mode of delivery has an impact on the progression to the second and third births but that a first delivery by vacuum extraction does not reduce the propensity of subsequent childbearing to the same extent as a first delivery by emergency or elective caesarean section. The fourth study explores the effects of parental death on adult children's fertility. The findings reveal that parental death during reproductive ages can affect children’s fertility. The effects are moderated by the gender of the child and when in the life course bereavement occurs. The combined output of these four studies provides evidence that human fertility behavior is embedded in social relationships with kin and friends throughout life. Family of origin, social background, an older sibling's birth, and bereavement following parental death influence the adult child's fertility. These findings add knowledge to previous research on intergenerational and social network influences in fertility.

  Read more about Parents, Children and Childbearing

• Mode of delivery and the probability of subsequent childbearing

  2015. Charlotte Elvander (et al.). British Journal of Obstetrics and Gynecology 122 (12), 1593-1600

  Article

  Objective: To investigate the relationship between mode of first delivery and probability of subsequent childbearing.

  Design: Population-based study.

  Setting: Nationwide study in Sweden.

  Population: A cohort of 771 690 women who delivered their first singleton infant in Sweden between 1992 and 2010.

  Methods: Using Cox's proportional-hazards regression models, risks of subsequent childbearing were compared across four modes of delivery. Hazard ratios (HRs) were calculated, using 95% confidence intervals (95% CIs).

  Main outcome measures: Probability of having a second and third child; interpregnancy interval.

  Results: Compared with women who had a spontaneous vaginal first delivery, women who delivered by vacuum extraction were less likely to have a second pregnancy (HR 0.96, 95% CI 0.95–0.97), and the probabilities of a second childbirth were substantially lower among women with a previous emergency caesarean section (HR 0.85, 95% CI 0.84–0.86) or an elective caesarean section (HR 0.82, 95% CI 0.80–0.83). There were no clinically important differences in the median time between first and second pregnancy by mode of first delivery. Compared with women younger than 30 years of age, older women were more negatively affected by a vacuum extraction with respect to the probability of having a second child. A primary vacuum extraction decreased the probability of having a third child by 4%, but having two consecutive vacuum extraction deliveries did not further alter the probability.

  Conclusions: A first delivery by vacuum extraction does not reduce the probability of subsequent childbearing to the same extent as a first delivery by emergency or elective caesarean section.

  Read more about Mode of delivery and the probability of subsequent childbearing

• Social Background and Becoming a Parent in Sweden

  2015. Johan Dahlberg. European Journal of Population 31 (4), 417-444

  Article

  In this study, I introduce three measures of social background, namely occupational class, social status, and parental education, into fertility research. The objective is to examine whether these dimensions of social background affect entry into parenthood even after controlling for several potential pathways. I estimate event history models on first birth rates using data, which include all Swedes born in 1960. The results show that each of the three dimensions of social background has a clear bivariate association with the risk of becoming a parent, both for men and for women. Parental education has the strongest effect of class and status background, and the latter two do not affect the entry into fatherhood when the effects of all dimensions of social background are estimated simultaneously. Much of the remaining association between social background and fertility persists when controlling for own educational history, mother's age at first birth, and father's mean incomes. The results also show that higher social background leads to postponement of childbearing but that it has no effect on the final likelihood of ever become a parent. The influence of social background on fertility is stronger for women than for men.

  Read more about Social Background and Becoming a Parent in Sweden

• Family influence in fertility

  2013. Johan Dahlberg. Demographic Research 29, 233-246

  Article

  BACKGROUND The intergenerational transmission of fertility has received much attention in demography. This has been done by estimating the correlation between parents' and offsprings' fertility. An alternative method that provides a more comprehensive account of the role of family background - sibling correlations - has not been used before. OBJECTIVE I estimate the overall importance of family background on entry into parenthood and completed fertility and whether it changed over time. Furthermore, I compare the intergenerational correlation in completed fertility with corresponding sibling correlations. METHODS Brother and sister correlations in first birth hazard and in final family size were estimated using multi-level event-history and multi-level linear regression on Swedish longitudinal register data. RESULTS The overall variation in fertility that can be explained by family of origin is approximately 15%-25% for women and 10%-15% for men. The overall importance of the family of origin has not changed over the approximately twenty birth cohorts that were studied (1940-63 for women, 1940-58 for men). Parents' completed fertility accounts for only a small share of the total family background effect on completed fertility. CONCLUSIONS This study contributes to the existing understanding of intergenerational transition of fertility, both methodologically, by introducing a new and powerful method to study the overall importance of family of origin, and substantially, by estimating the overall importance of family of origin and its development over time. A non-negligible proportion of the variation in fertility can be attributed to family of origin and this effect has remained stable over twenty birth cohorts.

  Read more about Family influence in fertility

Show all publications by Johan Dahlberg at Stockholm University