Measuring the unintended components of low fertility

Daniel Devolder, Universitat Autonoma de Barcelona

Low fertility in developed countries is associated with higher desired than achieved total cohort fertility. In this paper we propose to quantify the proportion of the difference between desired and achieved fertility due to what we call the 'unintended' components of low fertility, the postponement of motherhood and the greater instability of unions that characterized the last 25 years. We will use a microsimulation model of fertility with a set of biological parameters with constant values and a set of family behaviours with either constant or variable values. Contraceptive use will be associated with the pursuit of a desired number of children, and we will use models of the changes in union formation and dissolution behaviours in developed countries during the last 25 years. The wide range of simulated fertility levels will allow us to measure the importance of these unintended components of low fertility.