Transcript Ways to judge a journal Impact factor and other measures

Dilip R Karnad
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Circulation – number of
copies per month?
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Readership – many readers
per copy
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Regular readers – browse
current issues
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Referred to by researchers
or experts – specific articles
located by literature search
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Scientometrics or
Journalology
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1955 - Eugene Garfield in Science - Citation is key
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1961 – Institute for Scientific Information - Science citation index
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1992 – bought by Thomson Scientific – now Thomson-Reuters
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Impact factor =
Citations in current year to articles in previous 2 years
Number of articles published in previous 2 years
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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
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Number of years – current status = ?state of the art
Rank
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Abbreviated Journal Title
Cancer Journal for Clinicians
New England Journal of Medicine
Annual Review of Immunology
NATURE REVIEWS MOLECULAR CELL BIOLOGY
PHYSIOLOGICAL REVIEWS
REVIEWS OF MODERN PHYSICS
Journal of the American Medicel Association
NATURE
CELL
NATURE REVIEWS CANCER
NATURE GENETICS
ANNUAL REVIEW OF BIOCHEMISTRY
NATURE REVIEWS IMMUNOLOGY
NATURE REVIEWS DRUG DISCOVERY
LANCET
SCIENCE
NATURE MEDICINE
ANNUAL REVIEW OF NEUROSCIENCE
NATURE REVIEWS NEUROSCIENCE
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS
Impact Factor
74.575
50.017
41.059
35.423
35
33.985
31.718
31.434
31.253
30.762
30.259
30.016
30.006
28.69
28.409
28.103
27.553
26.405
25.94
25.826
Evaluation of quality of references cited
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Citation density - average number of
references cited in the new article
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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
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Immediacy Index is the average number of times an article is cited in the
year it is published.
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The journal Immediacy Index indicates how quickly articles in a journal
are cited.
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Immediacy Index = number of citations to articles published in 2008
number of articles published in the journal in 2008
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Frequently issued journals have an advantage.
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Can identify journals specializing in cutting-edge research.
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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
Specialty with large number of researchers/practitioners –
more citations
 Large specialty:
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 more authors, more articles, more citations – numerator
 more journals, more articles to cite – denominator
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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
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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
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Delay in manuscript acceptance, review and publication = low citation
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Many articles on same topic in one issue =increases citation of all
articles
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Long-term impact of articles missed – 5-year or 10-year IF
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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?
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Selective journal self citation: articles tend to preferentially cite other
articles in the same journal
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Self author self citations
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Review articles are heavily cited and inflate the impact factor of journals
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Long articles collect many citations and give high journal impact factors
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Short publication lag permits self citations - high journal impact factor
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Journal set in database may vary from year to year
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Impact factor is a function of the number of references per article in the
research field
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Owned by Garfield / ISI / Thomson Reuters
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Includes only journals indexed in “Current Contents”
– another ISI publication – “get indexed with us...”
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Coverage of the database is not complete
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Database has an English language bias
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Database is dominated by American publications
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Eigenfactor Project™ is a non-commercial academic research
project
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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.
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Committed to sharing findings with interested members of the
public, including librarians, journal editors, publishers, and authors
of scholarly articles.
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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.
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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:
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Counts citations to journals in both the sciences and social sciences.
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Eliminates self-citations. Every reference from one article in a journal
to another article from the same journal is discounted.
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Weights each reference according to a stochastic measure of the
amount of time researchers spend reading the journal.
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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.
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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
1:8 articles made
open-access
Davis PM, et al. Br Med J 2008;337:a568
Davis PM, et al. Br Med J 2008;337:a568
Google scholar citations
Vs
Science Citation Index
Favaloro EJ, Semin Thromb Hemost 2008;34:7–25
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