Volume 24 - Article 21 | Pages 497–526

Variance in death and its implications for modeling and forecasting mortality

By Shripad Tuljapurkar, Ryan D. Edwards

Print this page  Facebook  Twitter


Date received:01 Aug 2010
Date published:22 Mar 2011
Word count:8007
Keywords:entropy, inequality, proportional hazards


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 D. Edwards - City University of New York, United States of America [Email]

Other articles by the same author/authors in Demographic Research

» 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

Most recent similar articles in Demographic Research

» A behaviorally-based approach to measuring inequality
Volume 19 - Article 49    | Keywords: entropy, inequality

» The effects of family and location on wealth: A longitudinal study of the US North, 1850–1870
Volume 38 - Article 59    | Keywords: inequality

» State-level changes in US racial and ethnic diversity, 1980 to 2015: A universal trend?
Volume 37 - Article 33    | Keywords: entropy

» Disparities in death: Inequality in cause-specific infant and child mortality in Stockholm, 1878‒1926
Volume 36 - Article 15    | Keywords: inequality

» Differences in perinatal health between immigrant and native-origin children: Evidence from differentials in birth weight in Spain
Volume 35 - Article 7    | Keywords: inequality