The hypotheses are empirically tested through qualitative and quantitative micro- and macro-level analyses.
The first PhD student explores the project's themes on the basis of oral history interviews and other qualitative sources (e.g. ego documents, media discourse, (Church) reports). The other two PhD students examine the research questions on the basis of quantitative micro data; one by focusing on the historical period (cohorts born ca. 1850-1920) using historical population registers and civil registers, the other by investigating the contemporary period (cohorts born ca. 1920-1970) with data from current databases and surveys.
While the PhD students analyze different aspects of reproductive behavior separately (e.g. age at first birth, cumulative fertility) and for either the historical or contemporary period, the PI connects sources and investigates reproductive careers (i.e. histories of childbearing) for the entire period using sequence analysis. The PI also charts fertility indicators and their family system correlates on the regional and national level over the last 160 years and for the whole of Europe.
The qualitative and quantitative research on the micro-level consists of five phases related to the key relationships of the conceptual model:
Phase I: Dispersal of kinship networks
The micro-level projects start with an investigation of the extent to which members of the kinship network were proximate enough to provide support , engage in competition and exert social influence. Concretely, in this phase the team charts who lived nearby (same household, same locality, same region etc.) at the onset and during the course of childbearing. How did dispersal patterns vary across family systems and according to age, gender and social class, and how have these patterns changed over time?
Phase II: Resource provision, kin competition and reproductive behavior
In the next phase the researchers investigate how different types of available kin influenced various aspects of fertility behavior, such as the total number of children, birth intervals, age at starting, age at stopping, whole reproductive careers, as well as child survival. To what extent were different types of kin beneficial or detrimental to various aspects of reproductive behavior and to children's survival chances and how did this differ across family systems and over time?
Phase III: Intergenerational transmission of reproductive behavior
The third phase concentrates on processes of social learning and social pressure. The aim is to find out to what extent individuals learned from or conformed to their relatives' reproductive behavior and might have done so differently across family systems and over time. The researchers focus particularly on socialization through parents and study the intergenerational transmission of reproductive behavior.
Phase IV: Sibling interdependencies in reproductive behavior
In this phase, the project moves beyond parents in order to investigate the effects of social influence by siblings on reproductive behavior. What is the relative importance of social learning via siblings in comparison to intergenerational transmission via parents? Is it true that sibling effects vary across family systems? And to what extent has the relative importance of siblings changed during the twentieth century?
Phase V: Husband-wife relations and reproductive behavior
In the last phase the researchers focus on how gender roles and power relations between husband and wife shape(d) reproductive behavior. To what extent did the power balance between husbands and wives (measured for instance by their age homogamy) influence decisions in the wife's reproductive career? And how can differences in gender relations across family systems explain regional differences in fertility change?