Do siblings' fertility histories influence each other?

Alexia Fuernkranz-Prskawetz, Vienna Institute of Demography
Torkild Lyngstad, Statistics Norway

Individuals' fertility decisions are most likely shaped not only by their own characteristics and life course paths, but also by social interaction with others through social networks. However, in practice it is often difficult to disentangle the role of social interaction from other factors like individual and family background variables. We propose to measure social interaction through the cross-sibling effects on fertility. Continuous-time hazard models are estimated separately for the women's first and second birth intensities. In addition to individual socioeconomic and demographic variables and a sibship-specific unobserved factor, siblings' three first birth events and their timing enter as time-varying covariates. We use data from longitudinal population-wide Norwegian administrative registers. The data set includes the siblings' fertility, education, income and marital histories. Our results indicate that cross-sibling effects are relatively strong for the respondent's first births, but weaker for the second parity transition.