Dissertation

The fertility puzzle: trends and patterns of male and female fertility

Abstract

Human fertility is a complex and multifaceted phenomenon that has been studied extensively in demography. Despite its importance for population growth and structures, fertility remains a poorly understood aspect of human behavior, with many factors influencing whether and how many children an individual may have. Therefore, this thesis aims to shed light on the factors affecting fertility trends and patterns, with a focus on the interplay of social, cultural, economic, structural, and biological factors that influence human fertility. By considering the contributions of both men and women, and employing subnational designs to address the limitations of cross-country comparisons, this thesis aims to provide a nuanced understanding of the factors affecting fertility trends and patterns. The noteworthy decline in TFRs in the Nordic and Anglo-Saxon countries provides a timely motivation for this study, highlighting the need for a comprehensive analysis of the complex factors driving fertility changes. In Chapter 1, I describe the fertility trends across countries in the recent period and introduce the most important theories of fertility. In Part I, I focus on predictors of fertility at the macro-level. Chapter 2 describes the relationship between economic development and fertility in the United States using longitudinal data. Here, the fertility decline reversal as well as the fading relationship in the 2010s are particularly noteworthy. Chapter 3 uses Finnish register data to discern the contribution of accelerated secularization to the recent declines in fertility. This chapter advances also a sociological mechanism, the self-reinforcing effect of secularization on fertility, which rests on the interaction of religious affiliation, partnership formation and couple fertility. Chapter 4 of the thesis quantifies couples’ fecundity, an often overlooked but potentially relevant factor in childbearing. By combining data from the Norwegian Mother and Child Cohort Study (MoBa) with Norwegian register data, I predict couple’s sub-fecundity using modern machine-learning tools. Part II focuses on gender differences in fertility. Chapter 5 investigates male-female differences in subnational fertility rates across eight middle- and high-income countries. This chapter highlights the relevance of regional population imbalances on gender differences in fertility quantum. Moreover, it describes factors that lead to these gender differences and proposes four approaches to classify pronounced differences, e.g. birth squeezes. Chapter 6 harnesses individual-level Finnish register data to assess the relationship between life-time exposure to unbalanced regional partner markets and the probability of remaining childless among men. This chapter proposes partner markets as a potential driver for fertility trends, as men’s childlessness has been rapidly increasing, particularly among lower educated men. The thesis concludes in Chapter 7 with a discussion of the importance of fertility for society, potential policy suggestions, and provides a glimpse at the future of fertility.