The tertiary sector of the economy (also known as the service sector or the service industry) is one of the three economic sectors, the others being the secondary sector (approximately the same as manufacturing) and the primary sector (agriculture, fishing, and extraction such as mining).
The service sector consists of the "soft" parts of the economy, i.e. activities where people offer their knowledge and time to improve productivity, performance, potential, and sustainability. The basic characteristic of this sector is the production of services instead of end products. Services (also known as "intangible goods") include attention, advice, experience, and discussion. The production of information is generally also regarded as a service, but some economists now attribute it to a fourth sector, the quaternary sector.
The tertiary sector of industry involves the provision of services to other businesses as well as final consumers. Services may involve the transport, distribution and sale of goods from producer to a consumer, as may happen in wholesaling and retailing, or may involve the provision of a service, such as in pest control or entertainment. The goods may be transformed in the process of providing the service, as happens in the restaurant industry. However, the focus is on people interacting with people and serving the customer rather than transforming physical goods.
For the last 100 years, there has been a substantial shift from the primary and secondary sectors to the tertiary sector in industrialised countries. This shift is called tertiarisation. The tertiary sector is now the largest sector of the economy in the Western world, and is also the fastest-growing sector.
In examining the growth of the service sector in the early Nineties, the globalist Kenichi Ohmae noted that:
"In the United States 70 percent of the workforce works in the service sector; in Japan, 60 percent, and in Taiwan, 50 percent. These are not necessarily busboys and live-in maids. Many of them are in the professional category. They are earning as much as manufacturing workers, and often more. 
Examples of tertiary industries may include the following. :
Difficulty of definition
It is sometimes hard to define whether a given company is part of the secondary or tertiary sector.
In order to classify a business as a service, one can use classification systems such as the United Nations's International Standard Industrial Classification standard, the United States' Standard Industrial Classification (SIC) code system and its new replacement, the North American Industrial Classification System (NAICS), the Statistical Classification of Economic Activities in the European Community (NACE) in the EU and similar systems elsewhere. These governmental classification systems have a first-level hierarchy that reflects whether the economic goods are tangible or intangible.
For purposes of finance and market research, market-based classification systems such as the Global Industry Classification Standard and the Industry Classification Benchmark are used to classify businesses that participate in the service sector. Unlike governmental classification systems, the first level of market-based classification systems divides the economy into functionally related markets or industries. The second or third level of these hierarchies then reflects whether goods or services are produced.
Theory of progression
Economies tend to follow a developmental progression that takes them from a heavy reliance on agriculture and mining, toward the development of manufacturing (e.g. automobiles, textiles, shipbuilding, steel) and finally toward a more service-based structure. The first economy to follow this path in the modern world was the United Kingdom. The speed at which other economies have made the transition to service-based (or "post-industrial") economies has increased over time.
Historically, manufacturing tended to be more open to international trade and competition than services. However, with dramatic cost reduction and speed and reliability improvements in the transportation of people and the communication of information, the service sector now includes some of the most intensive international competition, despite residual protectionism.
Issues for service providers
Service providers face obstacles selling services that goods-sellers rarely face. Services are not tangible, making it difficult for potential customers to understand what they will receive and what value it will hold for them. Indeed some, such as consultants and providers of investment services, offer no guarantees of the value for price paid.
Since the quality of most services depends largely on the quality of the individuals providing the services, it is true that "people costs" are a high component of service costs. Whereas a manufacturer may use technology, simplification, and other techniques to lower the cost of goods sold, the service provider often faces an unrelenting pattern of increasing costs.
Differentiation is often difficult. For example, how does one choose one investment adviser over another, since they often seem to provide identical services? Charging a premium for services is usually an option only for the most established firms, who charge extra based upon brand recognition.
List of countries by tertiary output
Service output as a percentage of the top producer (USA) as of 2005 Bellow is a list of countries by service output in 2011.
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