What is/are the primary source of such data?

All demographic studies are based on processes of counting or enumeration – such as the census or the survey – which involve the systematic collection of data on the people residing within a specified territory.

Census: The procedure of systematically acquiring and recording information about the members of a given population. The term is used mostly in connection with ‘national population and door to door censuses’ to be taken every 10 years. For example, the Economic Census in India is a Central Sector Scheme, with 100% Central Assistance and is conducted in all the States and Union Territories of the country, in collaboration with State/UT Governments., The Economic Census data, over the years, have provided a base for under taking follow up surveys by NSSO and other governmental and non-governmental agencies to study the structure and composition of the various industrial sectors and their contribution.

Survey: The National Sample Survey Office (NSSO) in India is a unique setup to carry out surveys on socio-economic, demographic, agricultural and industrial subjects for collecting data

from house-holds and from enterprises located in villages and in the towns. It is a focal agency of the Govt. of India (under the newly created Ministry of Statistics and Programme Implementation (MOSPI)) for collection of statistical data in the areas which are vital for developmental planning.