What are the three broad categories of division of population on the basis of their economic structure?

(i) Children (generally below 15 years): They are economically unproductive and need to be provided with food, clothing, education and medical care.
(ii) Working age (15-59 years): They are economically productive and biologically reproductive. They comprise the working population.
(iii) Aged (above 59 years): They can be economically productive, though they may have retired. They may be working voluntarily, but they are not available for employment through recruitment.