What are impact factors and how would I use them?
A journal's impact factor is based on how often articles published in that journal during the previous two years (e.g. 2000 and 2001) were cited by articles published in a particular year (e.g. 2002). The higher a journal's impact factor, the more frequently articles in that journal are cited by other articles. The impact factor can therefore give an approximate indication of how prestigious a journal is in its field.
There are different measures of impact factors, taken across different numbers of years, so be careful that you are comparing like with like. Not all journals have impact factors, and the importance of impact factors will vary between disciplines. They nevertheless provide a useful pointer to the more important journals in your subject.
The Eigenfactor is another way to estimate a journal's standing within the academic community and it also counts numbers of citations to a journal, but it weights those from other high impact journals higher. In this way, it works similarly to Google's PageRank.
Instructions on how to find a journal's impact factor are given below.
How do I find a journal's impact factor?
Use the Journal Citation Reports (JCR) available through the Web of Knowledge service. To check the impact factor of a specific journal you can search by title. Otherwise, you can browse by subject (subject categories are brought together in the Science and Social Science strands).
You can sort the information in many different ways - you will most likely wish to rank journals according to their impact factor. In addition to the impact factor you can check other aspects of a journal, such as immediacy index (a measure of how soon after publication the "average" article is cited - useful in comparing how quickly different journals are cited).
The following is a list of high-impact journals based on impact factors (i.e. citation frequency) from the Journal Citation Reports (JCR) (available as part of the Web of Science) and from the The SCImago Journal Rank (SJR). The SCImago Journal Rank (SJR) indicator was developed by SCImago from the widely known algorithm Google PageRank™. This indicator shows the visibility of the journals contained in the Scopus® database from 1996.
Here is a quick summary of what to expect from the three best known citation analysis tools.
| Subject Focus |
Science, Technology, |
Science, Technology, Medical, Engineering, Arts & Humanities | Medical, Scientific, Technical, Business, Social Sciences, Arts & Humanities |
| Components |
Composed of several citation indexes:
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The majority of these titles go back to 2002 |
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| Coverage | Over 12,000 journals |
21,000 active journals 50,000 books 6.5 million conference papers 24 million patents |
Unknown |
| Time Span |
Some journal files going back to 1900; see above for more detail |
44.4 million records, of which:
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Theoretically, whatever is available on the Web |
| Updated | Weekly | Daily | Monthly on average |
| Strengths |
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| Weaknesses |
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Information on this page has been adapted from guides created at University of Ottawa Bibliotheque and University of Connecticut Library.
