Characterising life-span variability in a population using the life-table-based Lorenz-curve analysis.

Background: 'Life expectancy' (LE) is a health-status indicator in widespread use. However, LE is an index of central location, but not of dispersion. It cannot describe inter-individual variation in the life-span. This author proposes using the Gini coefficient, a summary index of the Lorenz curve, for characterising life-span variability. Like the LE, the proposed index is also based on a lifetable.

Method: The method is a nonparametric approach that does not make specific assumptions about mortality rates.

Results: The author uses vital statistics from Taiwan as a demonstration and finds that the method provides information crucial to the understanding of the epidemiologic transitions of the past 20 years (Gini decreases from 0.1320 to 0.1130). It also quantifies the impacts of elimination of some selected causes of death in Taiwan.

Conclusions: It is recommended that Gini be routinely compiled in official vital statistics, along with the LE.