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A one-stop shop for all your scholarly publishing needs.

Journal Impact Factors Explored

Three Impact Factor rating services compared:

1. Journal impact factors are found in Journal Citation Reports (JCR). JCR is a unique database which is used to determine the relative importance of journals within their subject categories.

An impact factor is one measure of the quality of a journal. This is calculated by the number of citations received by the journal, from other journals within the Web of Science database.

'A journal impact factor is the average number of times that articles published in a specific journal in the two previous years (eg 1998-99) were cited in a particular year (ie 2000).'

Tree, v. 14, no. 10, Oct. 1999, p 382. 

Impact Factor Calculation 

2. Scopus has an Analytics tab which allows you to compare the performance of up to ten journals. The main two measures are 

View this short four-minute video for an introduction to SJR and SNIP, by Dr Lisa Geitjenbeek-Colledge, Product Manager for SciVal:

[Elsevier Publishing, 2009.  “SJR and SNIP”. YouTube video, posted February 10, 2010. Accessed August 10, 2012.]

3. Journal h-index is one measure of the quality of a journal and can be calculated using data from Web of Science, Scopus or Google Scholar. As with the impact factor, journal h-index does not take into account differing citation practices of fields (unlike the weighted SJR and SNIP) and so is best used to compare journals within a field.

'An entity has an h-index value of if the entity has publications that have all been cited at least times'.

(Hodge & Lacasse 2011, p. 583)

Flexible publication window

While JCR's impact factor offers calculations based on windows of two and five years, and SJR and SNIP are based on three years, the h-index publication window can be selected to best suit the citation practices of a discipline. 

Information reused from University of South Australia Subject Guide licensed under Creative Commons Share Alike 4.0 

- Not all journals have impact factors. They must be indexed in Web of Science to have an impact factor, (8,000+ Science and 3,000+ Social Science journals).

- A journal has only one impact factor, but it may be listed in more than one category

- A journal impact factor should not be looked at in isolation, but in comparison to other journals in the same category

- Impact factors vary across disciplines 

- A five-year impact factor may also be used in some disciplines

Impact factors can be used to:

- Help identify journals in which to publish

- Help identify journals relevant to your research

- Confirm the status of journals in which you have published

But is it a good number? To state that the British Medical Journal (BMJ) has an impact factor of 14.093 is not meaningful

It is more useful to say that BMJ’s impact factor ranks sixth of 153 journals in the field of general and internal medicine. Or to compare the journal’s impact factor of 14.093 with the aggregate impact factor for its field: 3.919

It is recommended therefore that the impact factor for a journal is not looked at in isolation. Rather, the impact factor of a journal should be compared to the impact factors of other journals within the same subject category.

Information taken from University of South Australia Subject Guide licensed under Creative Commons Share Alike 4.0