Does Period Life Expectancy Overestimate Current Survival?

Michel Guillot, University of Wisconsin at Madison

Bongaarts and Feeney have recently argued that life expectancy at birth (e0) is a biased measure of current survival, because it is affected in part by tempo effects resulting from a shift in the schedule of cohort mortality. They calculate a modified life expectancy at birth, e0*, and conclude that e0 as conventionally calculated overestimates life expectancy. This paper argues that e0* should not be interpreted as an unbiased measure of mortality conditions of a period, net of tempo biases. Rather, it should be interpreted as an average measure of past cohort survival. Thus it is not surprising that, given mortality declines, current e0 overestimates e0*, but not for the reasons discussed by Bongaarts and Feeney. Finally, this paper questions the adequacy of making a strict parallel between fertility and mortality using the tempo concept.