The impact factor and other measures of journal prestige

The impact factor and other measures of journal
prestige

Helping you get published

The impact factor and other measures of journal prestige

It is a well known fact that academics worldwide face pressure to
publish in prestigious English language journals. And the journal
impact factor (IF) is the most widely recognized indicator of journal
prestige and influence. Accordingly, many people choose which
journals to publish in based largely on the IF. 1


Calculation of IF
The IF is basically a ratio. The 2010 IF is calculated as follows:2

IFX = All citations in 2010 to articles published in Journal X in 2009 and 2008
All citable articles published in Journal X in 2009 and 2008

As you might have guessed, IFs for 2010 become available only in 2011 and so on.
Journal IFs are calculated yearly and disclosed in the Journal Citation Reports (JCR)
published by Thomson Reuters.


Use and misuse of the IF
1. As an objective measure of journal prestige. There are a vast number of
journals to choose from, and the journals’ IF provides an objective measure of
the overall quality of work published in that journal. As a general rule, the
higher the IF value of a journal, the more prestigious it is considered to be.

2. To select journals for libraries. There are tens of thousands of journal
publications in existence. The IF provides library administrators with a tool to
decide which journals to retain in their collections and which new ones to
acquire for their libraries.

3. Academic evaluation. The IF is often used in the process of academic
evaluations of researchers for tenure, grants, funding, etc. However, this use is
incorrect because the IF is only meant to indicate the quality of an entire
journal, not the quality of individual articles published in the journal.3


Beware while using the IF
When using the IF to compare or assess journals, be on the lookout for the following:4,5

1. The absolute value of a journal’s IF is meaningless. For example, a journal with an IF
of 2 would not be very impressive in a subject like microbiology, but it would be in
oceanography. Specialty journals - like disease-specific journals or journals focusing
on disaster management - tend to have a low IF value because the journal articles are
mostly read and cited by a small specialized audience.6

2. Disciplinary trends are different. Citation habits vary across different research areas.
Therefore, IFs should not be used to compare journals across disciplines. For
example, citation frequency is much higher in medicine than in mathematics or
engineering; therefore, medical journals have higher IFs than mathematical and
engineering journals.7


Beware while using the IF
3. IFs are not very relevant in certain fields. For example, in computer science,
conference proceedings are considered the principal form of scientific publication.

4. Not having an IF doesn’t make a journal unworthy. Thomson Reuters calculates IFs
based on their citation database. The database indexes roughly half of the
approximately 25,000 peer-reviewed journals8 believed to be published. The
coverage of their database is unevenly distributed as well, with some subject areas
better indexed than others. In addition, although it indexes journals from 60
countries, there are not many publications from under-developed countries and only
a small number of journals that publish in languages other than English.


Changes in journal practice because of the IF
The IF is as important, if not more, for journal editors as for researchers. The IF is used to
measure journal performance, and many journal editors are under pressure to increase their
journal’s IF.9 Further, IFs can be manipulated.3,10-12 For example, review articles have been found
to attract the most number of citations, so journals may try to publish more review articles to
increase their IF. Journal editors may select articles on the basis of how likely they are to be
cited. Journals may also ask authors to cite other papers from the journal (called “self-
citations”).
Not so fun fact
This is one of the reasons that case reports,
which are not frequently cited, are difficult
to publish. Indeed, some journals have
ceased publishing case reports all together,
even though they can be highly useful to
readers.


Alternatives to the IF
The IF ruled the roost for several decades. However, alternative indicators of journal
prestige have been developed in recent years. It has been found that all of these
indicators correlate closely with each other. In other words, journal rankings based
on these indicators tend to be similar, though there may be differences in the
absolute journal rankings. So researchers should feel free to use any one of the
below indicators, and not limit themselves to the IF, when selecting journals to follow
or publish in.13-15


Scimago Journal Rank (SJR)
Data source: Scopus
Can be found at: http://www.scimagojr.com/ free

How it’s calculated: Citations from prestigious journals are given more weight than
citations from lower-tier journals (similar to Google’s PageRank algorithm). SJR for
2010 is calculated by counting 2010 citations to papers published in 2007, 2008, and
2009 (three-year period).

Why it’s useful: SJR indicates which journals are more likely to have articles cited by
prestigious journals, not simply which journals are cited the most.


Journal Impact Factor (JIF)
Data source: ISI Web of Science
Can be found in: Journal Citation Reports subscription required

How it’s calculated: All citations are given equal weight. The IF is calculated over a
two-year period.

Why it’s useful: It is the traditional and most widely accepted measure of journal
prestige. Most people in the academic world know about and use the JIF.


Source Normalized Impact per Paper (SNIP)
Data source: Scopus
Can be found at: http://www.journalindicators.com/ free

How its calculated: SNIP is computed so that citations are normalized by field. Thus, it
eliminates variations found in JIF wherein the IFs are high in certain fields and low in
others. They calculate several other metrics as well, like citation potential in the
journal’s subject field.

Why it’s useful: SNIP is a much more reliable indicator than the JIF for comparing
journals among disciplines. It is also less open to manipulation by journals.16


Eigenfactor score (ES) and Article Influence Score (AIS)
Data source: ISI Web of Science
Can be found at: http://www.eigenfactor.org/ free

How its calculated: ES is similar to SJR; it also gives greater weight to citations from
prestigious journals. ES is calculated over a 5-year period. Like SNIP, it also normalizes
citations by field. Finally, it tries to mathematically model the time that a researcher
spends with each journal. The AIS is similar to the IF, except the AIS is calculated using
the ES, making it a more robust calculation than the IF.

Why it’s useful: The evidence indicates that ES and AIS are more robust indicators of
journal prestige and influence than the IF. 14


Conclusion

The journal impact factor is a very useful tool for the evaluation of journals, but it must
be used wisely. The decision on which journal to send your manuscript to should not rest
solely on the IF. It is especially important to remember that a journal with a narrow focus
(e.g., Diagnostic Molecular Pathology) may have a lower IF than a more broad-based
journal (e.g., Journal of Pathology). Finally, researchers should look up other indicators
for journal quality, like SNIP and Eigenfactor score, to get a better idea of journal prestige
and influence.

REFERENCES:

1. Brischoux F & Cook TR (2009). Juniors seek an end to the impact factor race. BioScience, 59(8), 638-
9. doi: 10.1525/bio.2009.59.8.2.
2. Garfield E (1994). The Thomson Reuters impact factor. Last accessed: August 30, 2011. Available at:
http://thomsonreuters.com/products_services/science/free/essays/impact_factor/
3. For example, see Seglen PO (1997). Why the impact factor of journals should not be used for
evaluating research. BMJ, 314: 497-502.
4. Neuberger J & Counsell C (2002). Impact factors: Uses and abuses. European Journal of
Gastroenterology & Hepatology, 14(3), 209-11.
5. Adler R, Ewing J, Taylor P (2008). Citation statistics: A report from the International Mathematical
Union (IMU) in cooperation with the International Council of Industrial and Applied Mathematics
(ICIAM) and the Institute of Mathematical Statistics (IMS). Joint Committee on Quantitative
Assessment of Research. Available
at: http://www.mathunion.org/fileadmin/IMU/Report/CitationStatistics.pdf
6. Sloan P & Needleman I (2000). Impact Factor. British Dental Journal, 189: 1.
doi:10.1038/sj.bdj.4800583.
7. Podlubny I (2005). Comparison of scientific impact expressed by the number of citations in different
fields of science. Scientometrics, 64(1), 95-99. doi: 10.1007/s11192-005-0240-0.
8. House of Commons Science and Technology Committee (2011). Peer review in scientific
publications Vol 1. House of Commons: London, UK.

REFERENCES:

9. Smith R (2006). Commentary: The power of the unrelenting impact factor? Is it a force for good or
harm? International Journal of Epidemiology, 35: 1129-30. doi: 10.1093/ije/dyl191
10. Smith R (1997). Journal accused of manipulating impact factor. BMJ, 314: 461.
11. Sevinc A (2004). Manipulating impact factor: An unethical issue or an editor’s choice? Swiss Medical
Weekly, 134: 410.
12. Falagas ME & Alexiou VG (2008). The top-ten in journal impact factor manipulation. Archivum
Immunologiae et Therapiae Experimentalis, 56(4): 223-6. doi: 10.1007/s00005-008-0024-5.
13. Falagas ME, Kouranos VD, Arencibia-Jorge R, Karageorgopoulos DE (2008). Comparison of SCImago
journal rank indicator with journal impact factor. The FASEB Journal, 22(8): 2623-8. doi:
10.1096/fj.08-107938.
14. Rizkallah J & Sin DD (2010). Integrative approach to quality assessment of medical journals using
impact factor, eigenfactor, and article influence scores. PloS One, 5(4): e10204. doi:
10.1371/journal.pone.0010204.
15. Rousseau R, the STIMULATE 8 Group (2009). On the relation between the WoS impact factor, the
Eigenfactor, the SCImago Journal Rank, the Article Influence Score and the journal h-index. Available
from E-LIS archive, ID: 16448; http://eprints.rclis.org/16448/.
16. Moed HF (2011). The source-normalized impact per paper is a valid and sophisticated indicator of
journal citation impact. Journal of the American Society for Information Science and Technology,
62(1): 211-3. doi: 10.1002/asi.21424.

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The impact factor and other measures of journal prestige

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