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Primary vs. secondary Data

When conducting research, it’s important to understand the difference between primary and secondary data:

• Primary data refers to data you collect yourself specifically for your research question, through experiments, surveys, interviews, or fieldwork.
• Secondary data refers to data that has already been collected by other researchers or organizations, typically for a different purpose, but which you can reuse for your own research.

Reusing secondary data can save time, reduce costs, and enable comparisons across time, locations, or populations.

Search for existing datasets

Why use secondary data?

Using data collected by other researchers can greatly benefit your work:

• You may want to find data similar to yours, but collected in other places or during different time periods (for comparison or discussion).
• You may need to include datasets in a research project proposal.
• You may want to provide information in a publication without collecting new data yourself.

How to do it?

Check whether existing data is available that you can reuse—this can often be done by searching in dedicated data repositories or portals.

You can find datasets through several avenues, for example:

• Mendeley Data* is a platform where researchers share and find datasets.
• OpenAIRE offers a browser for research results and datasets from projects funded by the European Commission.
• re3data.org is dedicated to data repository searches. You can enter your research topic in the search bar and refine your results using filters (e.g., country, subject).
• Zanran.com is a search engine for statistics, tables, and figures. You can filter results by location, date, and file type (Excel, PDF, etc.). Note: downloading data requires free registration.
• Datasearch.elsevier.com* is a search engine similar to Scopus but focused on finding datasets and tables from research papers.
• Google Dataset Search can also be useful. Alternatively, you can use regular Google Search with Boolean operators.

Note: The use of these commercial sources (marked with *) is not officially validated by public authorities.

Go further

Are you using secondary data? Check out this information guide with best practices for data reuse:
https://www.openaire.eu/can-i-reuse-someone-else-research-data

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