Why do cohabiting couples marry? An example of a causal event history approach to interdependent systems

The purpose of this paper is to demonstrate a causal approach to interdependent systems based on two empirical investigations. These examples demonstrate (1) the study of two highly interdependent processes: entry into first marriage as the dependent process and the process of first birth/first pregnancy as the explaining one; (2) an interdependence occurring mainly in a very specific phase of individuals' lives (i.e. during the period of first family formation); (3) the involvement of time lags between cause and its effect (e.g. time until detection of conception); and (4) the highly dynamic character of an unfolding effect over time (i.e. the effect of first pregnancy/first birth on first marriage strongly depends on the progress of pregnancy and the time since the birth has taken place).