Secondary Data : Secondary data is that which has been collected earlier by an individual or institution and which have been published. The investigator just uses such data. If a investigator has collected some data earlier and another investigator uses the same data for investigation purpose, then this data will be secondary data for the second investigator, rather than being primary data. For example, if an investigator uses data which has been collected and published by the government in context to agriculture, labour, employment, etc. then such data will be considered as secondary data for him.

There are two main sources of secondary data :

I. Published source : From time-to-time government and non-government organisations collect the data on various topics and get them published. These published data is used by other people for their investigations. 

Following are the sources of published data:

• International Publications : Various international, government and private organisations get information published on various topics from time-to-time, like- International labour organisation, international monetary fund, etc. 
• Government Publications : Various ministries and departments of central government and state government get the data published on various topics from time to time. Such data is very trustworthy and important, 

For example : bulletin of reserve bank, annual reports of industries, etc. 

• Semi-Government Publications : Varoious semi-government organisations like municipalities, district council, panchayats, etc. gets the data published from time-to-time. 
• Reports of committees and commissions : Reports are presented and published by various committees and commissions formed by government. 
• Publications of commerical organisations : Big commericial organistions also get their data published which has been collected by their investigators and statistical departments. 

Example : Tata, Birla, Reliance, Unilever, etc. 

• Publications of Research Organistions : Various universities and research organisations get the result of their researches published like: Indian Statistical Institute, Indian Standards Institution, etc. 
• Papers and Magazines : Newspapers and magazines are also an important source of secondary data. From time-to-time important information on various topics gets published in newspapers and magazines. 

For example : Economic Times, Business standards, etc. publish important data frequently.

II. Unpublished Source : Universities, private institutions and individual researchers collect data for their own personal objective, but due to some reason, these data remain unpublished. These unpublished data can also be used as secondary data.