Volume 24 - Article 21 | Pages 497–526  

Variance in death and its implications for modeling and forecasting mortality

By Shripad Tuljapurkar, Ryan Edwards

Abstract

The slope and curvature of the survivorship function reflect the considerable amount of variance in length of life found in any human population. This is due in part to the well-known variation in life expectancy between groups: large differences in race, sex, socioeconomic status, or other covariates. But within-group variance is large even in narrowly defined groups, and changes substantially and inversely with the group average length of life. We show that variance in length of life is inversely related to the Gompertz slope of log mortality through age, and we reveal its relationship to variance in a multiplicative frailty index. Our findings bear a variety of implications for modeling and forecasting mortality. In particular, we examine how the assumption of proportional hazards fails to account adequately for differences in subgroup variance, and we discuss how several common forecasting models treat the variance in the temporal dimension.

Author’s Affiliation

• Shripad Tuljapurkar - Stanford University, United States of America EMAIL
• Ryan Edwards - University of California, Berkeley, United States of America EMAIL

Other articles by the same author/authors in Demographic Research

How does the demographic transition affect kinship networks?
Volume 48 - Article 32

Convergence in male and female life expectancy: Direction, age pattern, and causes
Volume 34 - Article 38

How can economic schemes curtail the increasing sex ratio at birth in China?
Volume 19 - Article 54

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