Conventional measures of age usually define people as 'old' at one chronological age, often 65. In many countries around the world, age 65 is used as a cutoff for everything from pension age to health care systems, as the basis of a demographic measure known as the 'old-age dependency ratio,' which defines everyone over 65 as depending on the population between ages 20 and 65.
In new study in the journal Population and Development Review, IIASA researchers Warren Sanderson and Sergei Scherbov provide new measures to replace the old-age dependency ratio.