Abhatoo - Centre Nationale de Documentation

The single most used demographic measure is the life expectancy at birth, but life expectancies at ages other than zero are also used in the study of human longevity. Our intuition tells us that the longest life expectancy is that of a new born. However, historically, the expectation of life at age one ( 1 e ) has exceeded the expectation of life at birth ( 0 e ). The crossover between 0 e and 1 e only occurred in the second half of the twentieth century in the developed world. Life tables for populations that have not achieved this crossing between life expectancy at birth and at age one are referred to here as imbalanced. The timing of this crossover is when infant mortality is equal to the inverse of life expectancy at age one. This simple relation between mortality at age zero and mortality after age one divides the world into countries that have achieved the crossover in life expectancies and those that have not. It is a within population comparison of mortality at infancy and after age one. However, results of these within comparison can be used for comparison between populations. For countries that have already achieved this crossing in life expectancies, the sex differential in the timing of the crossing is marked--females attain the crossing before males for every single population and in some cases by up to 20 years earlier. However, for most countries life expectancy at age one is still higher than life expectancy at birth and in some cases by several years. Subpopulation comparisons for the US show how black Americans are near to transitioning out of the imbalanced life table situation.