Related Experiment Video
Updated: May 11, 2026

Measurement of Lifespan in Drosophila melanogaster
Published on: January 7, 2013
The impossibility of separating age, period and cohort effects
1School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK. andrew.bell@bristol.ac.uk
Abstract:
This commentary discusses the age-period-cohort identification problem. It shows that, despite a plethora of proposed solutions in the literature, no model is able to solve the identification problem because the identification problem is inherent to the real-world processes being modelled. As such, we cast doubt on the conclusions of a number of papers, including one presented here (Page, Milner, Morrell, & Taylor, 2013). We conclude with some recommendations for those wanting to model age, period and cohort in a compelling way.
Related Concept Videos
Cross-Sectional Research
Longitudinal Research
Longitudinal Studies
Confounding in Epidemiological Studies
Bias in Epidemiological Studies
Two-Way ANOVA
The two-way ANOVA analysis initially begins by stating the null hypothesis that there is an interaction effect between the two factors of a dataset. This effect can be visualized using line segments formed by joining the means for...
