Demographic and sociological theories usually do not incorporate biological variable into their explanations. This dissertation addresses this void by examining the influence of age at menarche on age at first birth, the event of a first birth, and the number of children ever born (CEB). I expand on Demographic Transition theory by incorporating biology as one of the effects of modernization that has an effect on reducing fertility. Age at menarche decreases as a society modernizes. I use data from the 1995 Survey of Family Growth, Cycle V for the U.S., and the 1997 China Survey of Population and Reproductive Health. I further stratify the data into five race/ethnic groups: Chinese Han, Chinese minorities, U.S. Non-Hispanic Whites, U.S. Non-Hispanic Blacks, and U.S. Hispanics of Mexican origin. I use four different statistical methods to model my dependent variables: Ordinary Least Squares Regression, Cox Proportional Hazard Analysis, Poisson Regression, and Negative Binominal Regression. My first major finding is that the younger a woman is when reaching menarche, the younger she will be when giving birth to her first child. Second, the younger a woman is when reaching menarche, the longer the duration to a first birth and the less likely she is to experience a first birth. These two results are consistent in all the groups I analyze. Third, the younger a woman when reaching menarche, the fewer children she will produce. The U.S. Mexican-Origin women are an exception in this final outcome. It is well known that as a society modernizes, age at menarche decreases. Analyses in my dissertation indicate that as women’s ages at menarche decrease, their ages at giving birth to the first child also decrease, but their chances of having a first birth also decrease and their waiting time for having the first birth increases. Also, fertility will decline as age at menarche declines.

Demographic and sociological theories usually do not incorporate biological variable into their explanations. This dissertation addresses this void by examining the influence of age at menarche on age at first birth, the event of a first birth, and the number of children ever born (CEB). I expand on Demographic Transition theory by incorporating biology as one of the effects of modernization that has an effect on reducing fertility. Age at menarche decreases as a society modernizes. I use data from the 1995 Survey of Family Growth, Cycle V for the U.S., and the 1997 China Survey of Population and Reproductive Health. I further stratify the data into five race/ethnic groups: Chinese Han, Chinese minorities, U.S. Non-Hispanic Whites, U.S. Non-Hispanic Blacks, and U.S. Hispanics of Mexican origin. I use four different statistical methods to model my dependent variables: Ordinary Least Squares Regression, Cox Proportional Hazard Analysis, Poisson Regression, and Negative Binominal Regression. My first major finding is that the younger a woman is when reaching menarche, the younger she will be when giving birth to her first child. Second, the younger a woman is when reaching menarche, the longer the duration to a first birth and the less likely she is to experience a first birth. These two results are consistent in all the groups I analyze. Third, the younger a woman when reaching menarche, the fewer children she will produce. The U.S. Mexican-Origin women are an exception in this final outcome. It is well known that as a society modernizes, age at menarche decreases. Analyses in my dissertation indicate that as women’s ages at menarche decrease, their ages at giving birth to the first child also decrease, but their chances of having a first birth also decrease and their waiting time for having the first birth increases. Also, fertility will decline as age at menarche declines.

A large body of research has addressed women’s fertility with some among them focusing on East Asia. Relatively few studies concentrate on men’s fertility worldwide and almost none on South Korea. This study addresses the knowledge gap by exploring how men’s socio-economic status is associated with their transition to first child in South Korea. Data used for the analysis come from Korean Labor Income Panel Study. By applying logistic regression, I examine men’s entry into fatherhood by age 29 and 34. The study shows that men with post-secondary education are less likely to become a father by age 29 but more likely to become a father at higher ages than men with secondary education. Having only primary education generally lowers the odds of entry into fatherhood. Men’s employment engagement increases their odds of becoming a father by age 29 and by age 34 respectively, but there is more variation by workplace among younger men. The results suggest that higher socio-economic status, measured in educational level and employment status enhances fatherhood entry in South Korea.

In the 21st century, the division of housework remains gendered, with women on average still spending more time doing chores than their male partners. While research has studied why this phenomenon is so persistent, few studies have yet been able to assess the effect of gender ideology and socio-economic resources at the same time, usually due to data restrictions. We use data from the pairfam, a new and innovative German panel study, in order to test the effect of absolute and relative resources as well as his and her gender ideology on the division of housework. We employ a life course perspective and analyze trajectories of couples' housework division over time, using multi-level random effects growth curve models. We find that an egalitarian gender ideology of both him and her significantly predicts more egalitarian division-trajectories, while neither absolute nor relative resources appear to have an effect on the division of housework over time. Furthermore, our results expand the literature by investigating how these processes differ among childless couples and couples who experience the first birth.

Measuring the Effect of the Timing of First Birth on Mothers' Wages in the Czech Republic Magdalena Hummelová December 31, 2018 Abstract This thesis investigates the effect of fertility timing on women's long- run wages. Following the work of Herr (2016), by considering fertility timing in terms of labour market experience at the first birth, we study the effect on wages observed in the window 15 to 20 years after the labour market entry. This allows us to build different models for two groups of mothers: those entering the labour force with and without a child. We come to the conclusion that there is no effect of fertility timing for women entering the labour force already having a child. For women entering the labour force childless, the estimated postponement effect differs depending on whether they have an earning partner or not. If they do, there is clear cost of fertility delay by one more year (contrary to expectations) associated with a decrease in wages by 1%. This finding is very likely connected to a trend of lengthy parental leaves in the Czech Republic. If a woman does not have a partner, we observe an insignificant effect of first birth delay, yet positive. Comparing the results for women living in versus out of Prague, we see no significant difference in the effects.

Background: The total fertility rate (TFR) in South Korea has fallen below 1.3 since 2001. The role of the rapid shift toward a late-childbearing pattern in driving Korean fertility decline to this ultra-low level has been little explored until now. Objective: We provide an in-depth analysis of period fertility trends by birth order in South Korea from 1981 to 2015, when the period TFR fell from 2.57 to extremely low levels. Methods: We combine census and birth registration data to estimate period and cohort fertility indicators by birth order. We compare changes in conventional TFR with tempo- and parity-adjusted total fertility rate (TFRp*) and their birth-order-specific components. Results: The tempo effect linked to the shift toward delayed childbearing has had a strong and persistent negative influence on period TFRs in South Korea since the early 1980s. Without the shift to later childbearing, period fertility rates in South Korea would consistently stay higher and decline more gradually, reaching a threshold of very low fertility, 1.5, only in 2014. The postponement of childbearing and the resulting tempo effect were strongest in the early 2000s, when Korean TFR reached the lowest levels. More recently, Korean fertility has been characterized by a diminishing tempo effect and falling first and second birth rates. This trend marks a break with the previous pattern of almost universal fertility and a strong two-child family model. Contribution: Our study demonstrates the importance of the tempo effect in explaining the shift to ultra-low fertility in South Korea and in East Asia.

There are indications that young adults, and especially young parents, are inincreasingly economically challenging positions. Educational attainment is commonly used in research evaluating fertility behaviour, while less is known how the relationship between education and fertility has changed over time. Therefore, this thesis analyses the transition into parenthood among young adult men and women in Sweden over time, focusing on the role of education on fertility. Using an event history analysis framework, the transition to first birth among 20-25 year-olds in Sweden is analysed using the Swedish Generations and Gender Survey over the period 1980 to 2014. On average, men and women of lower education have a higher risk of entering parenthood between the ages of 20 to 25 compared to all other educational levels. However, the relationship seems to be conditioned on calendar period and gender, where the risk of entering parenthood between ages 20 to 25 is higher in the 1990s and 2000s compared to the 1980s among low educated men, where the opposite is true for women.

Background The debate regarding the lower age limit for mammography service screening is old and lively; a product in part of the lower breast cancer risk in younger ages as well as the limited data available for studies of the younger age group. Recently the idea of inviting only high risk groups has gained momentum, however high risk might not be equivalent to greater benefit from screening. Therefore, there is a need for information on effectiveness of screening as it relates to young women and to specific risk groups. To this end, this thesis evaluates mammography screening for the age group – 40 to 49 year old women – in terms of breast cancer mortality reduction in total and in subgroups based on breast cancer risk factors. Overdiagnosis of mammography screening is also evaluated for women 40 to 49 years old. In addition, this thesis presents a statistical method to estimate this effectiveness and to test for differences in effectiveness between subgroups adjusted for non-compliance and contamination. Methods The studies of this thesis are based on data from the Screening of Young Women (SCRY) database. The SCRY database consists of detailed information on diagnosis, death, screening exposure and risk factors for breast cancer cases and population size by year (between 1986 and 2005) and municipality for women in Sweden between 40 and 49 years old. The material was divided into a study group consisting of the counties that invited women in the age group 40-49 years to mammography screening, and a contemporaneous control group consisting of the counties that did not. Effectiveness was estimated in terms of rate ratios for two different exposures (invitation to and participation in screening), and overdiagnosis for subsequent screening was estimated adjusting for lead time bias. Defining a reference period enabled adjustment for possible underlying differences in breast cancer mortality and incidence. A statistical model for adjusting for non-compliance and contamination in randomised controlled trials was further developed to allow for adjustment in cohort studies using a Poisson model with log-linear structure for exposure and background risk. Results During the study period (1986-2005), there were 619 and 1205 breast cancer deaths and 6047 and 7790 breast cancer cases in the study group and the control groups, respectively. For women between 40 and 49 years old, the breast cancer mortality reduction was estimated at 26% [95% CI, 17 to 34%] for invited to screening and 29% [95% CI, 20 to 38%] for attending screening. The RR estimates for the high-risk groups based on the risk factors parity, age at birth of first child, and socio-economic status were equal to or higher than that of the low risk groups. The new statistical method showed that the decrease in effectiveness with parity was not a statistically significant trend. The overdiagnosis from subsequent screening for 40 to 49 year old women was estimated at 1% [95 % CI, -6 to 8 %] (i.e., not statistically significant). Conclusion Subgroup specific effectiveness was also estimated. The relative effectiveness of screening for breast cancer with mammography for women age 40 to 49 years appears to be comparable to that for older women. These findings and the fact that there was no statistically significant overdiagnosis from subsequent screening speak for inviting women 40 to 49 years old to screening. High-risk screening for nulliparous women aged 40 to 49 years, for example, might be an alternative in countries where population-based screening for all women between 40 and 49 years old is not possible. However, the matter of risk factors and the effect of their combinations is complex and risk group screening presents ethical and practical difficulties. The new statistical model is a useful tool for analysing cohorts with exposed and non-exposed populations where non-compliance and contamination is a potential source of bias.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

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.