Measuring the relative importance of determinants of coresidential fertility for recent birth cohorts across 7-19 countries with GGS II data using microsimulation

While demographic research has uncovered a wide range of determinants of fertility outcomes, it has been difficult to estimate the relative importance of these determinants. This is because the fertility process is complex, and many of the determinants of fertility outcomes are interdependent. It is therefore difficult to estimate independent effects of these determinants with statistical techniques commonly used in fertility research, like event history analysis and life table approaches. Another shortcoming in fertility studies is that the physiological constraints on human fertility have rarely been explicitly modelled, despite the fact that they are the most proximate determinants of fertility outcomes, and now more relevant than ever with increasing mean ages at first birth. We address these issues with a microsimulation model we developed that reproduces the entire reproductive life courses of individual women. The model includes information on reproductive physiology, reproductive behaviour, educational attainment, and union events. The reproductive physiology part of the model is based on modelling work by Henri Leridon and clinical data. For the behavioural part of the model, we use data mainly from the Generations and Gender Survey II. We apply our simulation model to a wide range of countries. By doing this we can not only uncover the most important determinants of fertility outcomes within each country, but we can also compare determinants between countries. What makes our approach different from statistical and life table approaches is that we explicitly model the mechanisms of the fertility process based on empirical data and fertility theory, and treat fertility as a process over the entire reproductive life course of a woman.