Statisticians miscalculate the number of elderly in the world: are there more or less than expected?

Thousands of elderly people are missing, announced the BBC article (2 July 2013). Where are they?

Life expectancy has been improving around the world in the last 20 years. On average, the global life expectancy has increased by 6 years. This has predominantly been due to improvements in child mortality in low and middle income countries. In developed countries, such as Britain and America, the life expectancy has increased rapidly.

In the 1980s, the life expectancy of men in Britain increased by 14 years in the 1990s, and then it increased by 21 years in 2011, according to the British 2011 population census. That’s a 50% increase in 30 years. So it means that now there should be a good proportion of elderly men in Britain, at least a lot more than would otherwise be expected. Right? Not quite. In the 2011 British population census there were 30,000 fewer people aged in their 90s than statisticians expected (they expected about 429,000, but there were only 457,000)—that’s 15% fewer men than expected, and 5% fewer females than expected. There were also fewer centenarians (people in the 100s) than expected. A similar occurrence happened in America. A 2004 projection suggested that by 2010 there would be about 114,000 people aged 100 or over, but in reality there were only half the amount.

Where have people over 90 years of age gone? They’ve gone to heaven. Much of them just didn’t live as long as statisticians expected.

The projections—the estimations of the life expectancy and the number of people in a particular age group—are determined by statisticians according to the figures from the previous population census and applying mortality tables and information from registered deaths and immigration data. So while data is used, the estimations are not exact; they are guesses. Especially since census data is taken only every 10 years. And a lot can happen in 10 years: natural disasters, air pollution, the spread of viruses, an epidemic, increased food intake, weather conditions (cold weather, hot weather etc.) and so on.

In addition, the total number of people over the age of 90 years in Britain and across the globe is relatively small. Hence any estimation errors can result in large discrepancies between the predicted number and the actual number. It turns out that statisticians were too optimistic about the expected numbers of 90+ year olds. This means that the 2021 British population estimates will be revised—and those across the globe.

Many countries have been adding between 2 to 3 years to their life expectancy every year for the past 30 years. Professor James Vaupel, director of the Max Planck Institute for Demographic Research in Germany, estimates that life expectancy globally has been increasing by 3 months each year, which is 6 hours per day. He says it’s actually been constant over the past 200 years of census data. The reasons, he says, were due to decreased child deaths, and deceased numbers of women dying during childbirth, but also due to the decreased smoking related and blood pressure related deaths.

However, the rapid rate of improved life expectancy can’t continue, can it? It’ll stabilize and become steadier, thinks the World Health Organisation.

The issue now is to ensure that people in the low to middle income countries have an increased life expectancy. Health improvements in Asia, Africa, and Latin America have been substantian over the past 20 years, but their life expectancy is still lower than in developed countries.

On average, life expectancy in Asia has increased by about 7 years since 1990, especially in India, China, Indonesia, the Philippines, and Malaysia. Eastern Mediterranean countries have also increased their life expectancy by 7 years since 1990. Countries in Africa have increased their life expectancy by 6 years (from 50 to 56 years of age) between 1990 and 2011, particularly in Nigeria with a 7 year increase.

However, malaria, HIV/Aids, child mortality, and maternal mortality are still issues in low to middle income countries. For example, in South Africa, the life expectancy has decreased by 5 years since 1990 (and 6 years in Zimbabwe).

The graph (from the World Health Organisation) shows that the global average life expectancy is 70 years. People in Europe, the Americas, and Western Pacific have a higher than average expected life of 76 years, while Africans have the lowest average life expectancy of 56 years.

http://www.bbc.co.uk/news/magazine-23126814