The study of the history of most of the developed countries shows that in the initial stages of development, the primary sector has been an important sector of economic activity. As modern technology started being used in the agricultural system, the agricultural sector became economically prosperous, production started increasing and people started getting attracted towards other works as well. The number of craftsmen and traders started increasing and the activities of buying and selling increased. People also got involved in transport, administration and military works. In this stage, most of the produced items were natural products which came in the primary sector and people used to work in this sector. As factories came into existence and factories started spreading, people started working in factories instead of farms. People started consuming good things produced in factories at cheap rates. In this way, gradually the importance of the secondary sector also increased from the point of view of total production and employment. If seen in the last 100 years, there has been a change again from secondary sector to tertiary sector in developed countries. Therefore, the importance of the service sector has also increased from the point of view of total production.