What is "dependency ratio"

n. (context geography English) The number of people under the age of 15 and over the age of 64 compared to the number of people active in the labor force.

In economics, geography, demography and Sociology the dependency ratio theory is an age-population ratio of those typically not in the labor force (the dependent part) and those typically in the labor force (the productive part). It is used to measure the pressure on productive population.