a measure of the portion of a population that is composed of people who are not in the work force and depend on others for support versus people who are in the work force and are self-sufficient. The dependency ratio is often defined in terms of age groups, with those who either are too young to work or are retired being set against those who are in their prime earning years; it is then calculated as the number of individuals aged below 15 or above 64 divided by the number of individuals aged 15 to 64.