Sectoral composition of an economy is the contribution of sectors such as the agricultural sector, service sector and industrial sector to the GDP of an economy.
Yes, it is necessary that the service sector should contribute maximum to the GDP of an economy. When an economy grows, there exists a situation called structural transformation. This implies that the economy's dependence on the agricultural sector will decrease to the minimum level and the share of the industrial and service sectors in the total GDP will increase over the years. The growth in the performance of the service sector with higher contribution to the total GDP is an indication of economic development.