Volume 23 - Article 26 | Pages 737-748

Attrition in heterogeneous cohorts

By James W. Vaupel, Zhen Zhang

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Date received:09 Apr 2010
Date published:12 Oct 2010
Word count:1779
Keywords:attrition, frailty, gamma distribution, Gompertz, heterogeneity, Makeham, mortality
DOI:10.4054/DemRes.2010.23.26
Weblink:All publications in the ongoing Special Collection 8 "Formal Relationships" can be found at http://www.demographic-research.org/special/8/
 

Abstract

In a heterogeneous cohort, the change with age in the force of mortality or some other kind of hazard or intensity of attrition depends on how the hazard changes with age for the individuals in the cohort and on how the composition of the cohort changes due to the loss of those most vulnerable to attrition. Here we prove that the change with age for the cohort equals the average of the change in the hazard for the individuals in the cohort minus the variance in the hazard across individuals. The variance captures the compositional change. This very general and remarkably elegant relationship can be applied to understand and to analyze changes with age in many kinds of demographic hazards, including, e.g., the lifetable aging rate or the intensity of first births.

Author's Affiliation

James W. Vaupel - Max Planck Institute for Demographic Research, Germany [Email]
Zhen Zhang - Fudan University, China [Email]

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