Secondary data is usually defined in opposition to primary data. The latter is directly obtained from first-hand sources by mean of questionnaire, observation, focus group or in-depth interviews, while the former refers to data collected by someone other than the user. In other words, data that has already been collected for some other purpose. Yet, such data may be very useful for your own research purpose.
A review of the literature accounts for many varieties of classification for secondary data (Bryman 1989, Dale et al. 1988; Robson, 202). Suffice it to mention Kervin classification (1992) who distinguish between raw data and compiled data. Regarding the former one, there has been little if any processing, while the latter one has received some form of selection or summarizing. Among the first type of secondary data it is worth mentioning those coming from organizations´ databases, organizations´ websites or newspaper, among other. Second type, compiled data, refers to for instance, government publications, books, journals or industry statistic and reports, among others.
There would be a third type of secondary data that is in between both raw and compiled, they were collected via survey strategy. For instance, census of population, continuous and regular surveys such as government family spending, labor market trends, employee attitude surveys, etc.; and last but not least, ad hoc surveys, i.e. those non-regular basis survey made by some organization.
Where is secondary data located? Your public or university library is still a great place to find relevant data for any project, especially with regard to books or encyclopedias. But the truth is that in the so called Internet society, a lot of worthy material is usually available via Internet or, at least, the references to such material. The use of key words may sometimes be enough to come across relevant secondary data via the most common search engine. However, the breadth of information on the net may be unmanageable or, what is worse, you may waste a lot of time on the always difficult task of discriminating between what is a bogus or a true research.
In this case it is highly recommendable to do customized searches via specific sources. Below are three kinds of sources that may help you on that venture:
1. Public statistical providers. Identify the main provider of statistical information, which is usually dependent on the government. Bureau of the Census of US or Central Statistical Office in the case of Poland. Find here a list of National Statistical Offices web-sites. The you have other international statistic offices such as Eurostat, where you will find social and economic indicators from all over the European Union members; as well as worldwide organizations such as OECD.Stat which includes data and metadata for OECD countries and selected non-member economies; or United Nations Statistic.
2. Specialized search engines. To use these you need to define your general subject area prior to your search. For instance, such database as Econlit count with their own search engine that focus only on economics and management publications, or The Financial Times Historical Archive in case of financial studies. Although the access to some of them may be for a fee, note that your own institution or University could perfectly be a subscriber. It is also worth mentioning Google Scholar. Its use is also becoming quite common within academia. It is not specialized in any particular subject, but discriminate efficiently among academics and non-academics publications. Finally, social networks are also shifting the way secondary data and review of literature is understood. Academia.edu is probably one of the most known and worldwide used academic networks. Counting with its own search engine, you can find not only relevant publications but also other scholars and professionals working on your topic.
3. Organizations related to your research topic. Finally, note that ample and relevant information may be obtained from organizations related to your research topic. Imaging your research focuses intellectual property issues. Visiting World Intellectual Property Organization is a must for you. The same would happen with the World Health Organization if you address health related issues. Equally when the focus is on a specific industry. Every industry normally counts with its own national and/or international organization. Euromines for minig, World Tourism Organization for the touristic industry. Should you happen to be interested on working rights, the International Trade Union Confederation (ITUC) website and, concretly, its global index report is an interesting source for you. Note that your topic, especially when is very specific, may not have any organization related. It may be due to two main reasons that should make you think over. First, your topic is not enough relevant and then you should consider another one. Second, your topic refers to a very new phenomenon and the interest lays on its emerging nature (Exploratory approach would be the most convenient for you)
Bryman, A. (2004). Research methods and organization studies (Vol. 20). Routledge.
Dale, A., Arber, S., & Procter, M. (1988). Doing secondary analysis (pp. 15-18). London: Unwin Hyman.
Kervin, J. B. (1992). Methods for business research. HarperCollinsPublishers.
Robson, C. (2002). Real world research: A resource for social scientists and practitioner-researchers (Vol. 2). Oxford: Blackwell.
Saunders, Mark NK, et al. Research Methods For Business Students, 5/e. Pearson Education India, 2011.