Reproductive behavior before the onset of the fertility transition: usage of the Cox regression and survival analysis for the study of birth intervals (case study of Jablonec, Bohemia, in the 18th century)

Ludmila Fialova, Charles University in Prague
Klara Hulikova Tesarkova, Charles University in Prague
Barbora Kuprova, Charles University in Prague

Knowledge of the length of the birth intervals in the past and factors influencing them could help us to reveal many aspects of the reproductive behavior in that time as well as about the aspects which significantly influenced family size, timing of births, etc. Study of the birth intervals is not among the most common research topics in demography, even in the historical demography itself. This is partly because of its significant data- and labor-demands. The aim of the paper is to describe the reproductive behavior in the families before the onset of the fertility transition using the survival analysis and the Cox regression. The methods were applied to individual observations acquired from the reconstitution of families (based on excerption of the parish registers). The presented case study focus on the locality of Jablonec, town in the Czech lands. The analyzed period covers the 18th century and partly also the 17th and 19th centuries. The influence of various explanatory variables (birth parity, age of the mother at marriage, age of the mother at the birth of the child, reversal birth order, surviving of child of previous order, total number of children born alive into a family) is quantified and tested. The results show that the birth intervals were affected above all by the length of the survival of the previous child, birth order of the child or age of the mother. The significant influence of the child or infant mortality and the effect of the limited fertile period of women were proved.