first ,the primary sector dominates\xa0second, when the people have sufficient food to eat they turn to manufacturing process i.e, secondary sectorthird, development of these two sectors provides various services which leads to the development of service sector
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Primary Sector1. As the method of farming changed and the agricultural sector began to prosper production increased.2. Many people could not take up other activities.3. It is the stage of the goods produced were natural products and most people employed in this sector.Secondary Sector1. Because of new methods of manufacturing were introduced, factories came up ang started expanding.2. Farmers began to work in factories.3.This sector slowly became the most important sector in the total production and employment.Hence a shift had taken place. It means the importance of sectors had changed.Tertiary Sector1. In the past 100 years there has been another shift from secondary to tertiary sector in the developed countries.2. The service has become the most important. in terms of total production.3. Most of the working people also employed in the service sector. These are observed in the developed countries