06 October 2017

Application of IIASA approach to UN projections shows less aging

The executive summary of the UN’s report on population aging, released today, incorporates new measures of aging developed at IIASA—leading to more optimistic projections for aging populations around the world.

© Vladimirs Prusakovs | Dreamstime

© Vladimirs Prusakovs | Dreamstime

A growing body of IIASA research shows that traditional measures of age do not capture the changing characteristics and capabilities of an aging population. Older people today are fitter and healthier than ever before, and living longer. Yet traditional population research assumes that people hit “old age” after an arbitrary cut-off of 60 or 65 years old.

Demographers at the institute have developed new approaches to measure aging based on people’s characteristics that for example, take into account increasing longevity. Those approaches were used to measure current and future aging based on population projections for almost all countries in the world up to 2100. Now these groundbreaking findings are being applied in the world’s leading international source of data on population aging.

“This is the first time that IIASA measures of aging are being incorporated in a UN official report,” says Warren Sanderson, a researcher at IIASA and Stony Brook University in the USA, who is part of the ERC-funded Reassessing Aging from a Population Perspective (ReAging) project which is led by IIASA World Population Program Director Sergei Scherbov. Sanderson says that this milestone reflects a growing recognition that traditional measures no longer reflect the changing face of aging around the world. The new UN report incorporates the IIASA approach to define a dynamic old age threshold based on changes in life expectancy—rather than a fixed chronological age.

Old-age and prospective old-age dependency ratio.

“When you incorporate our new measures, you get a completely different view of the future aging—it’s much more optimistic,” explains Scherbov. Projections using the new measures show for example, that the proportion of older people in the population could even decrease in many countries around mid-century.  This is not seen in projections that rely on traditional chronological age. 


Sanderson WScherbov S, & Gerland P (2017). Probabilistic Population Aging. PLoS ONE 12 (6): e0179171. DOI:10.1371/journal.pone.0179171.

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Last edited: 11 October 2017


Sergei Scherbov

Principal Research Scholar and Project Leader Social Cohesion, Health, and Wellbeing Research Group - Population and Just Societies Program


Warren Sanderson

Guest Research Scholar Social Cohesion, Health, and Wellbeing Research Group - Population and Just Societies Program



International Institute for Applied Systems Analysis (IIASA)
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