One classical breakdown of economic activity distinguishes three sectors:[1]

  • Primary: involves the retrieval and production of raw-material commodities, such as corn, coal, wood or iron. Miners, farmers and fishermen are all workers in the primary sector.
  • Secondary: involves the transformation of raw or intermediate materials into goods, as in steel into cars, or textiles into clothing. Builders and dressmakers work in the secondary sector.
  • Tertiary: involves the supplying of services to consumers and businesses, such as babysitting, cinemas or banking. Shopkeepers and accountants work in the tertiary sector.
Percentages of a country's economy made up by different sectors. Countries with higher levels of socio-economic development tend to have proportionally less of their economies operating in the primary and secondary sectors and more emphasis on the tertiary sector. The less developed countries exhibit the inverse pattern.
Three sectors according to Fourastié
Clark's sector model

In the 20th century, economists began to suggest that traditional tertiary services could be further distinguished from "quaternary" and quinary service sectors. Economic activity in the hypothetical quaternary sector comprises information- and knowledge-based services, while quinary services include industries related to human services and hospitality.[2]

Economic theories divide economic sectors further into economic industries.