The Interrelations Between Cohabitation, Marriage and First Birth in Germany and Sweden.

We study the interrelationships between union-formation forms and fertility in Swedish and West German female cohorts born in 1949-1971. We apply simultaneous hazard models, permitting the presence of correlated unobserved heterogeneity. This method allows us to control for country-specific composition of the population with respect to several socio-economic variables, as well as with respect to unobserved factors jointly affecting childbearing and union formation behavior. Our results confirm that partnership formation and the transition to parenthood are partially interchangeable. Net of those selection effects, we find that the impact of being in a union on first birth is higher in Sweden than in Germany, in particular for cohabitation. [ABSTRACT FROM AUTHOR]