Normalized lifespan inequality: disentangling the longevity\u2013lifespan variability nexus

Iñaki Permanyer,Jiaxin Shi

doi:10.1186/s41118-021-00150-6

Abstract

Previous studies have documented a historically strong and negative association between countries’ life expectancy (i.e., average longevity) and length-of-life inequality (i.e., variability in ages at death). The relationship between both variables might be partially explained by life expectancy increasing at a faster pace than maximal length of life, a phenomenon that mechanically compresses the age-at-death distribution and has not been taken into consideration in previous studies. In this paper, we propose a new approach to lifespan inequality measurement that accounts for the (uncertainly) bounded nature of length-of-life. Applying the new approach to the countries of the Human Mortality Database, we observe that the decline in overall lifespan variability typically associated with increases in longevity seems to stop and even reverse at higher levels of life expectancy. This suggests the emergence of worrying ethical dilemmas, whereby higher achievements in longevity would only be possible at the expense of higher lifespan variability.

Highlights

The past decades have witnessed an increasing interest in understanding the variation in length of life among demographers and researchers from other disciplines
We propose a new approach to lifespan inequality measurement that, unlike existing measures, explicitly takes into consideration the shrinking room for variability that ensues when both life expectancy and maximal lifespan get closer over time
In an attempt to adjust for such ‘boundary effect’, we propose a new approach to measure lifespan inequality

Summary

Introduction

The past decades have witnessed an increasing interest in understanding the variation in length of life among demographers and researchers from other disciplines (see, among others, Aburto & Van Raalte, 2018; Colchero et al, 2016; Edwards, 2011; Edwards & Tuljapurkar, 2005; Engelman et al, 2010; Gillespie et al, 2014; Nau & Firebaugh, 2012; Seaman et al, 2019; Seligman et al, 2016; Smits & Monden, 2009; Van Raalte & Caswell, 2013; Van Raalte et al, 2014, 2018; Vaupel et al, 2011; Wilmoth & Horiuchi, 1999). Studies have identified a historically strong and negative association between life expectancy (i.e., average longevity) and length-of-life inequality (Colchero et al, 2016; Edwards, 2011; Permanyer & Scholl, 2019; Smits & Monden, 2009; Vaupel et al, 2011, 2021; Wilmoth & Horiuchi, 1999). The mechanisms explaining such association have received considerable attention from recent demographic research. Nigri and colleagues (2021a, 2021b) found that the strength of this association is related to the location and speed when a country moves along the life expectancy distribution

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Conclusion