A nation’s economy can be divided into various sectors to define the proportion of the population engaged in different activities. This categorization represents a continuum of distance from the natural environment. The continuum starts with primary economic activity, which concerns itself with the utilization of raw materials from the earth, such as agriculture and mining. From there, the distance from natural resources increases.
Primary Sector
The primary sector of the economy extracts or harvests products from the earth, such as raw materials and basic foods. Activities associated with primary economic activity include agriculture (both subsistence and commercial), mining, forestry, grazing, hunting and gathering, fishing, and quarrying. The packaging and processing of raw materials are also considered to be part of this sector.
In developed and developing countries, a decreasing proportion of workers is involved in the primary sector. Only about 2 percent of the U.S. labor force is engaged in primary sector activity today, a dramatic decrease from the mid-19th century when more than two-thirds of the labor force consisted of primary-sector workers.
Secondary Sector
The secondary sector of the economy produces finished goods from the raw materials extracted by the primary economy. All manufacturing, processing, and construction jobs lie within this sector.
Activities associated with the secondary sector include metalworking and smelting, automobile production, textile production, the chemical and engineering industries, aerospace manufacturing, energy utilities, breweries and bottlers, construction, and shipbuilding.
In the United States, a little less than 15 percent of the working population is engaged in secondary sector activity.
Tertiary Sector
The tertiary sector of the economy is also known as the service industry. This sector sells the goods produced by the secondary sector and provides commercial services to both the general population and to businesses in all five economic sectors.
Activities associated with this sector include retail and wholesale sales, transportation and distribution, restaurants, clerical services, media, tourism, insurance, banking, health care, and law.
In most developed and developing countries, a growing proportion of workers is devoted to the tertiary sector. In the United States about 80 percent of the labor force is tertiary workers.
The Bureau of Labor Statistics puts non-agriculture self-employed into its own category, and that accounts for another 5 percent of workers, though the sector for these people would be determined by their job.
https://www.thoughtco.com/sectors-of-the-economy-1435795