London, 19 December 2010

World population passed 6.9 billion in mid-2010, according to United Nations demographers, and is on track to reach 7 billion in late 2011. The number of people added to the population each year – 79.3 million – has been consistent for nearly a decade. Since the world population is larger each year, of course, this consistent increment equates to a slow fall in the annual growth rate. From mid-2009 to mid-2010, the population grew 1.16%, compared with 1.32% annually a decade earlier and with slightly more than 2% four decades ago.

At the same time, humanity’s median age is consistently rising, a byproduct of longer life expectancy and the fact that women are having fewer children on average than their mothers had. In 1970, the world’s median age – the precise age at which half of all people are younger and half are older – was 22.1 years. In 2010, it is 29.1 years. Yet overall “youthening” was the consistent trend from 1950, when the median age was 24 years, until 1970. Since then the median age has risen by two to three months every year, a trend that now shows no signs of slowing.

The overall growth and aging of human population mask an unprecedented range of demographic diversity. Many industrial countries are now experiencing either relatively slow population growth or– in Japan, Germany, and 14 East European countries – absolute decline. The combination of rising life expectancy and falling fertility has led these countries to experience significant population aging, meaning a rise in the median age.

In contrast, many developing countries continue to grow rapidly and have still-large proportions of young people. Median ages are nonetheless rising slowly (albeit from low bases) in most of these countries for the same reasons as in industrial nations: increasing life expectancy and declining fertility. Some developing countries already have relatively low fertility accompanied by fairly rapid aging, with China being the most often discussed example.

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