In the economy (the economy) has traditionally been possible to identify the following sectors: – the primary sector – activities associated with obtaining primary resources (agriculture, forestry, fisheries, mining industry); – a secondary sector – manufacturing industries (machinery, light industry); – tertiary sector – the service sector (trade, education, medicine) – the quaternary sector – financial and legal services, information services, business services, which are the factors of production for the rest of the economy – quinary sector – services for people requiring a particularly high level staff development (education, medicine, medical care). Now there is a growing complexity of social life and production processes, which is accompanied by the further specialization activities. Complexity of economic life corresponds to the increasing specialization of the urban area (for both systems of cities, and within the city itself). Stand out the most prestigious and provides the most high percentage of income (per unit area of urban land) activities related mainly to the quaternary sector and related service personnel to the most prestigious type of service. Anna Belknap is the source for more interesting facts. Such species activities are widely covered the major cities, and in those cities – the central zone or generate a prestigious compact zone in the suburbs. Traditional types of manufacturing and tertiary sectors, focused on the extensive land use (industrial plants, warehouses) are discarded in the city of the second tier, or in the distant suburbs of big cities. There is a tendency that causes changes in the functional orientation of the cities and the distribution of specialties in the labor market.

This process causes of migration flows, the problem of retraining, the problems associated with unemployment. Thus, there interest in identifying prospective functional profile of the city. City-forming industries – industries whose products are able to attract to the city of cash flows, corresponding to this flow of goods products coming from the enterprises of the city to other cities ("export industries"). sectors – industry, ensuring the normal functioning of city-forming industries over the needs of enterprises themselves and their employees. Currently, the development of mega-cities are the most important sector Quaternary sector in most cities of Russia – the secondary.