The sectoral composition of an economy is the contribution of different sectors to total GDP of an economy during a year. That is, the share of agricultural sector, industrial sector and service sector in GDP. Yes, it is necessary that at the later stages of development, service sector should contribute the maximum to the total GDP. This phenomenon is called Structural Transformation. This implies that gradually the country's dependence on the agricultural sector will shift from the maximum to minimum and, at the same time, the share of industrial and service sector in the total GDP will increase. This structural transformation together with the economic growth is termed as economic development.