Presence-Impact Decomposition

Stable population theory provides an analogy in which population age distribution represents presence and reproductive value represents impact. Many perturbation sensitivities can be framed as the extent or probability of being affected multiplied by the impact on affected individuals. For lifespan perturbations without reproduction, candidate presence measures include survivorship, life table age composition, and death density. The note suggests expressing perturbation sensitivities as a presence term multiplied by an impact term.