title: The impossibility of separating age, period and cohort effects.
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.
authors.affiliation: School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK. andrew.bell@bristol.ac.uk
authors.forename: Andrew
authors.initials: A
authors.lastname: Bell
authors.forename: Kelvyn
authors.initials: K
authors.lastname: Jones
mesh_terms: D004651:Employment / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D013405:Suicide / Q000706:statistics & numerical data*
keywords: Age–period–cohort models; Collinearity; Model identification