The classical breakdown of all economic sectors follows: Primary: Involves the retrieval and production of raw materials, such as corn, coal, wood and iron. (A coal miner and a fisherman would be workers in the primary sector.) Secondary: Involves the transformation of raw or intermediate materials into goods e.g. manufacturing steel into cars, or textiles into clothing. (A builder and a dressmaker would be workers in the secondary sector.) Tertiary: Involves the supplying of services to consumers and businesses, such as baby-sitting, cinema and banking. (A shopkeeper and an accountant would be workers in the tertiary sector.) In the 20th century, it began to be argued that traditional tertiary services could be further distinguished from “quaternary” and quinary service sectors. An economy may include several sectors (also called industries), that evolved in successive phases. The ancient economy was mainly based on subsistence farming. The industrial revolution lessened the role of subsistence farming, converting it to more extensive and monocultural forms of agriculture in the last three centuries. Economic growth took place mostly in mining, construction and manufacturing industries. In the economies of modern consumer societies, services, finance, and technology – the knowledge economy – play an increasingly significant role. Even in modern times, developing countries tend to rely more on the first two sectors, compared to developed countries.