Demography

, Volume 52, Issue 1, pp 315–327 | Cite as

The Non-uniqueness Property of the Intrinsic Estimator in APC Models

  • Ben Pelzer
  • Manfred te Grotenhuis
  • Rob Eisinga
  • Alexander W. Schmidt-Catran
Article

Abstract

This article explores an important property of the intrinsic estimator that has received no attention in literature: the age, period, and cohort estimates of the intrinsic estimator are not unique but vary with the parameterization and reference categories chosen for these variables. We give a formal proof of the non-uniqueness property for effect coding and dummy variable coding. Using data on female mortality in the United States over the years 1960–1999, we show that the variation in the results obtained for different parameterizations and reference categories is substantial and leads to contradictory conclusions. We conclude that the non-uniqueness property is a new argument for not routinely applying the intrinsic estimator.

Keywords

APC Identification problem Intrinsic estimator Effect coding Dummy variable coding 

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Copyright information

© Population Association of America 2014

Authors and Affiliations

  • Ben Pelzer
    • 1
  • Manfred te Grotenhuis
    • 1
  • Rob Eisinga
    • 1
  • Alexander W. Schmidt-Catran
    • 2
  1. 1.Sociology and Social Sciences Research MethodsRadboud University NijmegenNijmegenThe Netherlands
  2. 2.Institute of Sociology and Social PsychologyUniversity of CologneCologneGermany

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