We’ve seen amazing improvements in life expectancy over the past few decades.

Six years have been added to global average life expectancy at birth, over the past two decades.

Much of this increase has been down to improvements in child mortality in low- and middle- income countries.

But in countries like the UK, post-retirement life expectancy has also increased rapidly.

“Life expectancy of a man aged 65 has increased from 14 years in the early 1980s to 21 years now – so that’s a 50% jump in just three decades,” says Richard Willets, director of longevity at insurance company Partnership.

Which is why, when the 2011 census was published, he went straight to the statistics about elderly populations.

And there the data revealed a surprise.

“There were 30,000 fewer people aged in their 90s than previously believed,” he says – 429,000 instead of 457,000.

“That was about 15% fewer men; 5% fewer females. There were also fewer centenarians than previously believed – the number of female centenarians was [out] by about 10%.”

Something similar has happened in the United States.

A projection made in 2004 suggested that by 2010, there would be around 114,000 people aged 100 or over, Willets says.

But, in reality, the 2010 census counted less than half that number.

Where have they all gone? …

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