ways to judge a journal impact factor and other measures
TRANSCRIPT
Ways to judge a journal
Impact factor and other measures
Dilip R Karnad
What is a good journal?
Circulation – number of
copies per month?
Readership – many readers
per copy
Regular readers – browse
current issues
Referred to by researchers
or experts – specific articles
located by literature search
Scientometrics or
Journalology
Journal impact factor
1955 - Eugene Garfield in Science - Citation is key
1961 – Institute for Scientific Information - Science citation
index
1992 – bought by Thomson Scientific – now Thomson-Reuters
Impact factor = Citations in current year to articles in previous 2 years
Number of articles published in previous 2 years
Journal impact factor =Number of articles (2007,2008) from the journal cited by any journal in 2009
Number of articles published in that journal in 2007,2008
Number of years – current status = ?state of the art
Impact factors 2008
Rank Abbreviated Journal Title Impact Factor
1 Cancer Journal for Clinicians 74.5752 New England Journal of Medicine 50.0173 Annual Review of Immunology 41.0594 NATURE REVIEWS MOLECULAR CELL BIOLOGY 35.4235 PHYSIOLOGICAL REVIEWS 356 REVIEWS OF MODERN PHYSICS 33.985
7Journal of the American Medicel Association 31.718
8 NATURE 31.4349 CELL 31.253
10 NATURE REVIEWS CANCER 30.76211 NATURE GENETICS 30.25912 ANNUAL REVIEW OF BIOCHEMISTRY 30.01613 NATURE REVIEWS IMMUNOLOGY 30.00614 NATURE REVIEWS DRUG DISCOVERY 28.6915 LANCET 28.40916 SCIENCE 28.10317 NATURE MEDICINE 27.55318 ANNUAL REVIEW OF NEUROSCIENCE 26.40519 NATURE REVIEWS NEUROSCIENCE 25.94
20ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS 25.826
Are other parameters required?
Evaluation of quality of references cited Citation density - average number of
references cited in the new article Half-life - number of retrospective
years required to find 50% of the cited references New England Journal of Medicine:
Cited Half-Life: 7.3 years
JIF add-ons - Immediacy Index Immediacy Index is the average number of times an article
is cited in the year it is published.
The journal Immediacy Index indicates how quickly articles in a journal are cited.
Immediacy Index = number of citations to articles published in 2008
number of articles published in the journal in 2008
Frequently issued journals have an advantage.
Can identify journals specializing in cutting-edge research.
New England Journal of Medicine
Cites in 2008 to items published in 2008 = 4352
Number of items published in 2008 = 356
Immediacy index = 12.225
Problems with JIF: Specialty Specialty with large number of
researchers/practitioners – more citations Large specialty:
more authors, more articles, more citations – numerator more journals, more articles to cite – denominator
JIF - Basic sciences journals >> Clinical journals Lowry OH, Rosebrough NJ, Farr AL, et al. Protein measurement
with the folin phenol reagent. J Biol Chem. 1951;193:265-275. Cited 300,000 times Southern EM. Detection of specific sequences among DNA
fragments separated by gel-electrophoresis. J Mol Biol. 1975;98:503-517.
Cited 30,000 times
Problems with JIF: Skewness
Skewness of citations The so-called 80/20 phenomenon
20% of articles account for 80% of citations
Citation rates in 1986 or 1987 of articles published in 3 biochemical journals in 1983 or 1984, respectively
Seglen, P. O BMJ 1997;314:497
Problems with JIF
Delay in manuscript acceptance, review and publication = low citation
Many articles on same topic in one issue =increases citation of all articles
Long-term impact of articles missed – 5-year or 10-year IF
Types of articles: research, review, letters, commentaries, perspectives, news stories, obituaries, editorials, interviews, and tributes
JAMA published 1905 items - 680 were letters and 253 were editorials.
Cited in same year – not included in numerator
Exclude from denominator?
What if cited in numerator in later years?
Problems with JIF
Selective journal self citation: articles tend to preferentially cite other articles in the same journal
Self author self citations
Review articles are heavily cited and inflate the impact factor of journals
Long articles collect many citations and give high journal impact factors
Short publication lag permits self citations - high journal impact factor
Journal set in database may vary from year to year
Impact factor is a function of the number of references per article in the research field
Problems with JIF: commercial
Owned by Garfield / ISI / Thomson Reuters
Includes only journals indexed in “Current
Contents” – another ISI publication – “get
indexed with us...”
Coverage of the database is not complete
Database has an English language bias
Database is dominated by American
publications
Alternatives to JIF - Eigenfactor Eigenfactor Project™ is a non-commercial academic
research project
Sponsored by the Bergstrom lab in the Department of Biology at the University of Washington.
Aim to use recent advances in network analysis and information theory to develop novel methods for evaluating the influence of scholarly periodicals and for mapping the structure of academic research.
Committed to sharing findings with interested members of the public, including librarians, journal editors, publishers, and authors of scholarly articles.
The Eigenfactor Score measures the number of times articles from the journal published in the past five years have been cited in the JCR year.
Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles. However, unlike the Impact Factor, the Eigenfactor Score:
Counts citations to journals in both the sciences and social sciences.
Eliminates self-citations. Every reference from one article in a journal to another article from the same journal is discounted.
Weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal.
Alternatives to JIF – Eigenfactor Score
Alternative to JIF: Article Influence Score
Article Influence Score calculates measures the relative importance of the journal on a per-article basis.
It is journal's Eigenfactor Score divided by fraction of articles published by the journal.
That fraction is normalized so that the sum total of articles from all journals is 1.
The mean Article Influence Score is 1.00. Score > 1.00 = each article in journal has above-
average influence. Score < 1.00 = each article in the journal has below-
average influence.
Alternatives to JIF – Impact of Internet
Webometrics Hits = readership, What is the meaning of downloads? Scholar Google – gives citations
What is the significance? Cites only from journals? Citation from websites included? May not include only peer-reviewed
citations “Sitations”
Perneger TV. Br Med J 2004;329:546–7
Impact of Internet – Hits = Citations ?
Davis PM, et al. Br Med J 2008;337:a568
1:8 articles made open-
access
Davis PM, et al. Br Med J 2008;337:a568
Favaloro EJ, Semin Thromb Hemost 2008;34:7–25
Google scholar citationsVs
Science Citation Index
BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)
BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)
BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)
Thank You