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Ways to judge a journal Impact factor and other measures

Ways to judge a journal Impact factor and other measures

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Ways to judge a journal Impact factor and other measures

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  1. Ways to judge a journalImpact factor and other measures Dilip R Karnad

  2. 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

  3. 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

  4. Impact factors 2008

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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?

  10. 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

  11. 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

  12. 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.

  13. Alternatives to JIF – Eigenfactor Score • 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.

  14. 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'sEigenfactorScore 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.

  15. 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”

  16. Impact of Internet – Hits = Citations ? Perneger TV. Br Med J 2004;329:546–7

  17. 1:8 articles made open-access Davis PM, et al. Br Med J 2008;337:a568

  18. Davis PM, et al. Br Med J 2008;337:a568

  19. Google scholar citations Vs Science Citation Index Favaloro EJ, SeminThrombHemost 2008;34:7–25

  20. BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)

  21. BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)

  22. BMJ, doi:10.1136/bmj.38422.611736.E0 (published 12 April 2005)

  23. Thank You