Explain the concept of 'occupational structure' with regard to population studies

Explain the concept of ‘occupational structure’ with regard to population studies.

The distribution of the population according to different types of occupation is referred to as " the occupational structure. Occupations can be classified as primary, secondary and tertiary.
Primary activities include those activities that are related to processing the natural resources of a country such as agriculture, animal husbandry, forestry, fishing, mining, quarrying etc.

Secondary activities include changing the primary resources into more useful form, therefore manufacturing industry, building, construction work comes under it. Tertiary activities include ; those activities that support the primary and secondary activities such as transport, communication, commerce, administration and other services.