Born Once - Die Once · Towards a transdisciplinary demographic theory of birth and death trajectories

Fertility and mortality fuel population renewal. Fertility theory struggles with a multitude of underlying, entangled dimensions, whereas mortality theory can build on strong regularities. Intriguingly, strong regularities analogous to death begin to emerge for birth, shown with my novel born once—die once approach. The Gompertz Law of death appears to apply to birth as well. The linear rise in record life expectancy seems to be mirrored by a linear rise in record ‘birth expectancy’ over decades. Thus encouraged, I propose to harness the power of mortality modeling to (1) add an unexplored, innovative dimension to fertility modeling and (2) develop a shared theoretical framework of birth and death trajectories that applies across the social sciences by conceptualizing different ‘types of individuals’ that are ‘born’ and ‘die’. I strive to achieve Ambition 1 by investigating birth with eight established regularities of death, modeling emerging patterns, and extending existing models of population renewal. Broadening the scope, Ambition 2 applies the approach of Ambition 1 to case studies of couples, families, and households, which I consider ‘social individuals’. I will define types of social individuals along shared dimensions and components rooted in cross-disciplinary perspectives of what defines an individual. Much will be learned from feasible empirical analysis in (1) and (2) about new relationships that can support and invigorate existing formal and empirical demographic research. If I master the conceptual challenges of this proposal, a shared and mirrored theoretical framework of birth and death will contribute a new and powerful toolbox for formal demographic analysis. Together with a generic concept of individuality, it would pioneer a new, transdisciplinary field of research that synergistically investigates the basic principles of formation, dissolution, and renewal, strengthening the theoretical foundation of population sciences.