Am I Halfway? Life Lived = Expected Life
We have reached halfway in life when our age equals our remaining life expectancy at that age. This relationship in stable population models between life lived and life left has captured the attention of mathematical demographers since Lotka. Our paper aims to contribute to the halfway-age debate by showing its time trends under mortality models and with current data from high longevity countries. We further contrast the halfway-age results by sex, and between period and cohort perspectives. We find that in 1850 life expectancy at birth was higher than halfway-age by around 10 years (HMD-mean halfway-age of 33.3 and 32.2 against HMD-mean life expectancy of 44.3 and 41.4 for women and men respectively). Nevertheless, declines in mortality at young ages radically changed life expectancy and it is found today at the same level as the double of halfway-age. While the period perspective puts halfway-age for females and males at 41.8 and 39.5 in 2010, for cohorts born in 2010 this might be as high as 10 years more. The stage of midlife has always been considered an important step in the life of human beings. However, there is no agreement on which is the age or age-range that represents the middle phase. Here we have further added the notion that halfway-age is not a static index but a moving age. Current and future progress in reducing mortality at older ages will require redefining our notion of midlife.
KeywordsLife expectancy Midlife Halfway-age Lotka Mortality models Mortality measures
We would like to thank Robert Schoen, Michel Guillot, Carlo Giovanni Camarda and the Max Planck Odense Center group for their comments and suggestion on how to improve our study.
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