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Born Once – Die Once: Towards a Transdisciplinary Demographic Theory of Birth and Death Trajectories

Birth and death are the cornerstones of existence. Complicated processes and random events determine why and when individuals are born and die. Yet, scientists have identified major regularities, especially for death. Here, we search for similar, yet unknown macro level regularities in childbirth. Applying the novel “born once – die once” approach, this project seeks to provide the foundation for better forecasting models of population dynamics in the future. We aim to pioneer a new, transdisciplinary field of research that synergistically investigates the basic principles of formation and dissolution, of renewal and aging, across systems and scales.


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, the project proposes 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’.

We 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 we consider ‘social individuals’. We 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 we 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.


Funded by the European Union (ERC, Born Once – Die Once, Grant agreement ID 101043983). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.

Annette Baudisch

Principal investigator

Meet the researcher

Last Updated 21.02.2024