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.