From Lifespan Inequality to Lifespan Inequity

This article introduces a comprehensive framework for defining and quantifying lifespan inequity within a population, grounded in the capability approach. Lifespan inequity (i.e., unfair inequality) is defined as lifespan deprivation due to premature mortality in a life table distribution of ages at death. We introduce the concept of the Minimally Adequate Length of Life as the threshold distinguishing premature deaths from lifespans of “normal length” and propose to quantify it with the adult modal age at death. Further, we propose to quantify lifespan inequity applying the widely used poverty indices from the Sen-Shorrocks-Thon and Foster-Greer-Thorbecke families, which consider the proportion of the life table cohort who die prematurely (incidence), the extent of their lifespan deprivation (depth), and the distribution of the deprivation among those who die prematurely (distribution). To demonstrate the utility of this approach, we apply the framework to quantify lifespan inequity in the United States from 1933 to 2021 and compare it with levels and trends in other high-income countries. The analysis shows that while US lifespan inequity initially declined faster than in other nations, it stagnated from the 1980s onward, resulting in the highest levels by the 2010s, with the COVID-19 pandemic exacerbating lifespan inequity through a sharp rise in the depth of premature mortality. We demonstrate that the measure of lifespan inequity developed in the proposed framework effectively defines, quantifies, and, therefore, assesses the ethical dimensions of inequality in the length of life within a population. This study highlights the essential interplay between demography and philosophy, as philosophical concepts underpin the assumptions and decisions that shape demographic measures and their interpretations.