The structure of population is the most basic characteristic of population. The general structure of population of a country is as fallow
(i) Children (below 15 years of age)
(ii) Working age (15 year-59 years)
(iii) Aged (60 year above)
This structure is the index of development in the fallowing ways
(i) The age of person influences what he needs, buys,does and his capacity to perform.
(ii) Children and aged people are the dependent population. They do not produce and depend upon the working age people. -
(iii) The working age people are economically productive and biologically reproductive.
(iv) A high working age population means low dependency ratio.
(v) High working population will earn more and can live in a better way.
Therefore, the development of a country is depended upon its working age population.
For example, If a person is of 35 years and he has 2 children aged 3 year and 7 year and 2 aged parents aged 69 and 74 years. He has to spend his earning among 4 - dependents. So, he will have very little to save. But if both he and his wife (aged 30 years) earn and they have only a child and 2 parents, then they have to spend less and could save more.
Therefore, , the structure of population is the index of the development of the country.