Tempo effects may distort the interpretation of trends in life expectancy

Recently, a new interpretation problem of trends in period life expectancy has been discussed in the demographic literature. The so-called tempo effects arise if large numbers of deaths are suddenly postponed. In such conditions, the life table inflates longevity gains in the population because it weights avoided deaths with the full remaining life expectancy. This article explains how such effects occur and indicates their relevance using an illustrative example.

Data of East and West Germany from the Human Mortality Database for the years 1990-2009 were used. We simulated a scenario that contrasts the observed life expectancy in West and East Germany with an alternative one based on the assumption of short-term postponements of deaths.

Our example demonstrates that if tempo effects have distorted changes in life expectancy, the pace of improvement in underlying mortality conditions could be over- and underestimated.

We recommend that the assumptions of the life table, in this case about the remaining life expectancy of avoided deaths, are carefully evaluated in all applications. Interdisciplinary efforts to develop models to detect and quantify tempo effects from life expectancy calculations should be put on the research agenda.