<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations . Please help to improve this article by introducing more precise citations . (August 2008) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations . Please help to improve this article by introducing more precise citations . (August 2008) (Learn how and when to remove this template message) </Td> </Tr> <Table> <Tr> <Th> Economic sectors </Th> </Tr> <Tr> <Th> Three - sector model </Th> </Tr> <Tr> <Td> Primary sector: raw materials Secondary sector: manufacturing Tertiary sector: services </Td> </Tr> <Tr> <Th> Additional sectors </Th> </Tr> <Tr> <Td> Quaternary sector: information services Quinary sector: human services </Td> </Tr> <Tr> <Th> Theorists </Th> </Tr> <Tr> <Td> AGB Fisher Colin Clark Jean Fourastié </Td> </Tr> <Tr> <Th> Sectors by ownership </Th> </Tr> <Tr> <Td> Business sector Private sector Public sector Voluntary sector </Td> </Tr> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table>

What are the three sectors of the us economy