Life Expectancy at Current Rates vs. Current Conditions

Abstract

Life expectancy is overestimated if mortality is declining and underestimatedif mortality is increasing. This is the fundamental claim made byBongaarts and Feeney (2002) in their article "How Long Do We Live?",where they base their claim on arguments about "tempo effects onmortality". This Reflexion explains why this claim is true in mostheterogeneous populations. It suggests that demographers should becareful about distinguishing between life expectancy under currentconditions, which is difficult and problematic to assess, and lifeexpectancy at current rates, which can be estimated using standardmethods. Finally, it speculates that there may be a deep connectionbetween tempo and heterogeneity.