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MPIDR Working Paper

A new approach to understanding the socio-economic determinants of fertility over the life course

Bijlsma, M. J., Wilson, B.

MPIDR Working Paper WP-2017-013, 29 pages (May 2017).
Rostock, Max Planck Institute for Demographic Research

Keywords: fertility, fertility determinants, socio-economic conditions, statistical analysis

Abstract

Most theories of fertility predict that a range of socio-economic factors have an impact on the quantum and tempo of childbearing. Despite this, methods often struggle to investigate the interrelationships between these factors, and the time-varying influence that they have on fertility over the life course. In this study, we propose a new approach for studying the socio-economic determinants of fertility. This approach uses the parametric g-formula, which enables analyses of simultaneous and interdependent influences of time-varying socio-economic factors (such as education, employment and partnership) on fertility. Importantly, and unlike many other approaches, this method allows us to incorporate reverse causality and time-varying confounding in a study of total, direct, and indirect (mediating) effects. It also enables these effects to be generalized to a heterogeneous nationally-representative population, linking micro- and macro-level analyses, while avoiding the ecological fallacy. To demonstrate this approach, we study a cohort of women who were born in the UK in 1970. Our results show that a significant reduction in fertility rates would be produced by a reduction in marriage rates, and to a lesser extent by a rise in either education participation or full-time employment immediately after giving birth. For marriage, the majority of this effect is direct, rather than mediated by either education or employment. We conclude our analysis by demonstrating the sensitivity of results to unobserved confounding. We then discuss how our approach can be developed and applied in future research in order to provide researchers with a valuable tool for the analysis of total effects and mediation in studies of correlated life course processes.

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