Capturing Demographic Burden Over Time with the Cumulative Dependency Ratio

The age dependency ratio is widely used to summarize population structure and to inform discussions of economic potential and population aging. However, as a period measure, it reflects the demographic balance at a single point in time and is highly sensitive to the timing of fertility and mortality change. This paper introduces the cumulative dependency ratio, a longitudinal reinterpretation of the traditional indicator that aggregates person‐years lived in dependent and support ages over a specified horizon. By explicitly incorporating the temporal dimension, the cumulative dependency ratio provides a person‐year‐based summary of demographic burden and facilitates comparison across periods, regions, and demographic scenarios. Using examples for the United States alongside comparative analyses across world regions, the paper illustrates how a cumulative perspective smooths short‐term demographic fluctuations, reduces sensitivity to the choice of observation year, and reframes the relationship between population structure and long‐run economic performance. Viewed through this cumulative framework, future fertility changes primarily affect the timing of dependency rather than its cumulative magnitude, and long‐run differences in demographic burden across regions appear smaller than implied by period measures. The cumulative dependency ratio complements existing indicators by providing an interpretable summary of sustained demographic pressures and intergenerational balance.