Regularities and peculiarities of birth schedules in industrialized countries: an analysis of FFS data

Inter-individual diversity of women according to birth numbers (quantum) and birth spacing (tempo) are important for understanding of fertility regimes. Elsewhere, we have shown that diversity with respect to fertility quantum is increasing from older to younger cohorts. The present study looks at tempo dimension by decomposing the diversity of birth schedules. The data set contains pooled FFS data from 19 industrialized countries and covers 11124 women aged 40-44 at survey. The analyses include descriptive characteristics of birth schedules, their classification by cluster analysis, and the identification of some of the underlying factors by two types of regression analyses. The first of them is a multinomial logistic regression linking types of birth schedules with characteristics of women at the time of interview. The second includes event-history analyses examining the transition to second and third conception (leading to birth), where time since previous birth is combined with the current values of the covariates. Age at first birth is a major component of inter-individual differences in birth schedules and it largely determines their clustering. Distributions of second, third, and fourth births over time since the previous births are very similar to each other. The median length of birth intervals is 3-3.5 years and 75% of births occur within 5-6 years after the previous delivery. One cluster stands out of this regularity as it is characterized by long last birth interval of about 11 years. Age distributions of fertility for women from this cluster are bimodal and their shape points at unexpectedly “renewed” fertility careers. Additional births produced by the phenomenon compose about 6% of all births. Regression analyses show that the long last birth interval is associated with new partnerships. Some influence of contraceptive failure can not be excluded, too. More in-depth research is needed to learn about the dynamic factors of birth schedules and particularly about the relationship between entering new partnerships and childbearing.