for National Geographic News
Higher life expectancy and falling birth rates have raised alarm bells in developed countries, where many analysts fear future generations could be financially crippled by the cost of supporting a graying population.
Yet a new study suggests the situation isn't nearly as bad as it seems. The report adds that current generations needn't make massive changes to the way they live to avoid becoming a burden on society in their old age.
This finding is based on the idea that the number of years people have livedthe current way a population's average age is estimatedis less important than the number of years people have left to live.
Having redefined average age, the researchers have come up with new predictions of how the proportion of elderly dependents will change in developed countries, including the United States, Germany, and Japan.
The study, which will appear tomorrow in the journal Nature, suggests populations can effectively become "younger" through increases in life expectancy.
The study was led by Warren Sanderson and Sergei Scherbov. Both are senior research scholars with the World Population Program at the International Institute for Applied Systems Analysis in Laxenburg, Austria.
"We propose a new age concept, called a person's prospective age," the researchers write. "Prospective age is a forward-looking concept, based on the person's remaining life expectancy."
Here's an example of how this concept works: If the remaining life expectancy for a 30-year-old in 2005 is the same as for a 40-year-old in 2055, then the future 40-year-old can expect to stay alive for as many more years as a 30-year-old today can expect to live.
When applied to a country like Germany, this new method puts a whole new perspective on things. The average age in Germany is expected to rise by around 12 years between 2000 and 2050, suggesting a rapidly aging population. But when remaining life expectancy (the new model) is taken into account, there's little change.
Older Middle Age
"Middle age in Germany, which came around the age of 40 in 2000, will come around age 52 in 2050," Sanderson said.
In the case of the U.S., on the basis of prospective age, Sanderson and Scherbov's calculations suggest the population may actually get "younger."
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