dependency ratios

Meaning: The dependency ratio is a demographic measure of how many presumed dependents each group of working-age people supports. It can be split into a youth dependency ratio (children) and an old-age dependency ratio (older adults). Societies early in the demographic transition, with high fertility, tend to have a high youth ratio. Societies with low fertility and long life expectancy tend to have a rising old-age ratio, which strains pension and health-care systems.

Equation: Dependency ratio = [(P0–14 + P65+) ÷ P15–64] × 100, where P0–14 is the number of people aged 0–14, P65+ is the number aged 65 and over, and P15–64 is the number aged 15–64 (all in persons). The result is dimensionless, read as dependents per 100 working-age people. Age cutoffs differ slightly between sources.

On the MCAT: A passage gives age-structure data or a population pyramid for one or more countries. You are asked which has the higher ratio, or how falling birth rates or longer life expectancy would change it. Falling fertility first lowers the youth ratio. Later, as the large cohort ages, the old-age ratio rises.

Common confusion: The ratio uses age, not actual employment. An employed 70-year-old still counts as a dependent, and an unemployed 30-year-old counts as working-age. A high ratio also does not have a single cause, because it can come from either end of the age distribution.