Working females : a modern statistical approach

The thesis analyzes the changing employment and economic situation of females when they become mothers. Two major questions are focused in the thesis: First, when do mothers return to their previous employment after bearing a child? Secondly, what are the individual economic consequences after having returned to the labor market? Both questions are analyzed empirically with latest statistical methods. The first major part of the thesis, corresponding to the above first motivated question, investigates maternity leave behavior in West Germany for females being employed between 1995 and 2006 using data from the German Socio Economic Panel. The observational study focuses on the investigation of individual and family-related covariate effects on the duration of maternity leave following first or second childbirth, respectively. Dynamic duration time models are used in which covariate effects are allowed to vary smoothly with duration of being in maternity leave. The intention of this part is to demonstrate with state of the art models how effects of covariates change over time and to analyze substantial differences between maternity leaves following first and second childbirth. Particularly the personal income of mothers and the educational attainment influence the decision when to return into employment. The leave period following second birth is influenced by the mothers attachment to the labor market between their two maternity leave periods. As fitting routine penalized spline smoothing effects is employed using available software in R (www.r-project.org), controlling for unobserved heterogeneity with a discrete mixture approach. The second major part of the thesis, corresponding to the secondly motivated question, investigates female wage profiles in West-Germany between 1984 and 2008 using again data from the German Socio Economic Panel. The empirical study focuses on the short-run wage loss due to childcare and the long-run wage-profile in post-birth employment, respectively. This is compared with wage profiles from females who are not mothers. As statistical analysis tool Additive Mixed Models are employed and estimated separately for different levels of educational achievements. The models are dynamic in that main covariate effects are allowed to vary smoothly with working experience. The intention of this chapter is to demonstrate with state of the art statistical models how wages are affected by labor market experience, employment interruptions and other covariates. The educational level of the mother and the time off the job influence the amount of wage loss and the wage profile afterwards. Labor market experience, as one major determinant of human capital, influences wages heavily and follows a dynamic pattern. Unobserved heterogeneity is taken into account by including individual random effects yielding an Additive Mixed Model. The fitting routine, employing penalized splines, is again carried out using the software package R.