One frequently used index for summarizing international age distributions is the dependency ratio, or the ratio of the dependent - age population (young or old) to the working age popu lation. The higher this ratio , the greater the burden of support on working people in specific geographic areas . In general, researchers have used dependency ratios to consider whether a population has too many “non - productive” persons (i.e . , young and old) relative to the working - age population, and the estimate s are typically viewed as consolidated function s of mortality, fertility, and net migration.