Dilip R Karnad

 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

 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

RankAbbreviated Journal TitleImpact Factor 1Cancer Journal for Clinicians New England Journal of Medicine Annual Review of Immunology NATURE REVIEWS MOLECULAR CELL BIOLOGY PHYSIOLOGICAL REVIEWS 35 6 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

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

 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 =

 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:  Cited 300,000 times  Southern EM. Detection of specific sequences among DNA fragments separated by gel-electrophoresis. J Mol Biol. 1975;98:  Cited 30,000 times

 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

 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 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?

 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

 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

 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.

 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  Score > 1.00 = each article in journal has above-average influence.  Score < 1.00 = each article in the journal has below-average influence.

 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

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 citations Vs Science Citation Index

BMJ, doi: /bmj E0 (published 12 April 2005)

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