The BBC News website recently featured a quiz based on Hans Rosling’s TV show, The Truth about Population. Judging by the results, people in Britain have a relatively poor understanding of how much life expectancy has increased over the last few decades. At present, average life expectancy in the world is approximately 70 years. However, 56% of respondents thought that it was 60 years or lower. And 76% of university graduates thought it was 60 years or lower. Only 30% of respondents, and only 20% of university graduates, gave the correct answer of 70 years.
In this post, I will present a few graphs depicting how life expectancy at birth changed between 1960 and 2010. All data are from the World Bank. Although life expectancy at birth is a good overall measure of a population’s mortality, it is quite sensitive to infant mortality, meaning that it may not be a good measure of how long someone who has already survived to age 5, say, can expect to live. Indeed, as a number of authors (e.g., Edwards, 2011) have pointed out, much of the increase in life expectancy at birth is attributable to a decline in infant mortality.
The first graph plots average life expectancy at birth over 186 countries (representing ~99% of the world’s population) between 1960 and 2010. The value for each year is a weighted average, with weights corresponding to population sizes (The trend is essentially identical without weights). In 1960, the average person could only expect to live about 52 years, whereas in 2010, she could expect to live nearly 70 years. The increase in life expectancy was particularly rapid during the 1960s and early 1970s (see Preston, 1980).
The second graph plots average life expectancy at birth in four regions of the developing world between 1960 and 2010. (Latin America comprises 20 countries, South East Asia 11 countries, South Asia 7 countries, and Sub-Saharan Africa 46 countries. Once again, values are weighted averages.) In all four regions, life expectancy increased substantially. The average person in Latin America saw an improvement of nearly 20 years; the average person in South East Asia of over 20 years; the average person in South Asia of over 20 years; and the average person in Sub-Saharan Africa of nearly 15 years. Progress in Sub-Saharan Africa stalled during the 1990s, due to the AIDS epidemic (see Logie, 1999). But it then recovered during the 2000s.
The third graph plots the distribution of life expectancy changes between 1960 and 2010 for 186 countries. All countries except one saw an improvement. In Zimbabwe, life expectancy unfortunately decreased by just under 2 years. The average improvement was over 15 years. And the maximum improvement, in the Maldives, was 39 years. 50% of countries saw an improvement of at least 15 years. And 25% saw an improvement of at least 20 years. For further discussion, see Wilson (2001).
The final chart plots change in the standard deviation of life expectancy at birth between 1960 and 2010 (n = 186). The standard deviation of life expectancy was nearly 20% lower in 2010 than it had been in 1960, which indicates that between-country variation in life expectancy decreased considerably over the period. Divergence occurred during the 1990s, due mainly to the AIDS epidemic in Sub-Saharan Africa (Moser et al., 2005). However, convergence re-established itself during the 2000s.
Edwards, R. D. (2011). Changes in world inequality in length of life: 1970-2000. Population and Development Review, 37(3):499-528.
Logie, D. (1999). AIDS cuts life expectancy in Sub-Saharan Africa by a quarter. British Medical Journal, 319:806.
Moser, K., Shkolnikov, V., Leon, D. A. (2005). World Mortality 1950-2000: Divergence replaces convergence from the late 1980s. Bulletin of the World Health Organization, 83:202-209.
Preston, S. H. (1980). Causes and Consequences of Mortality Declines in Less Developed Countries during the Twentieth Century. In Richard A. Easterlin (ed.). Population and Economic Change in Developing Countries. University of Chicago Press, Chicago.
Wilson, C. (2001). On the Scale of Global Demographic Convergence 1950-2000. Population and Demographic Review, 27(1):155-171.