The Crossover between Life Expectancies at Birth and at Age One: The Imbalance of the Life Table

Vladimir Canudas-Romo, Johns Hopkins University

Historically, the expectation of life at age one (e1) has exceeded the expectation of life at birth (e0). The crossover between e0 and e1 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. This is illustrated in the paper with several examples.