How is occupational structure classified?

How is occupational structure classified? Explain.

The distribution of the population according to different types of occupation is referred to as the occupational structure.
Different occupations can be classified into three groups
(i) Primary occupation These inculde agriculture, animal husbandry, forestry, fishing, mining and . quarrying etc.
(ii) Secondary occupation These include the manufacturing industry, building and construction works etc.
(iii) Tertiary occupation These include transport, communication, commerce, administration and other services.