1. Impact factorcillin®: hype or hope for treatment of academititis? Acknowledgement Seglen O Per (BMJ 1997; 134:497)

2. Outline ● Concept & applications of Journal Impact Factor ● Limitations and biases of the index ● Alternative approach

3. Journal Impact Factor ● introduced by Eugene Garfield (1955) as a simple method for comparing journals ● later be used for evaluating quality of scientific works ● evaluating individual researchers (academics) ● ranking schools or universities ● also be used for resource allocation in academic circle e.g. granting proposals, budget allocation among departments or universities

4. Journal Impact Factor ● Calculation – Numerator: number of citations in a certain year to papers in the same journal in the two years before – Denominator: number of ‘citable’ items published in that journal in the same two years

5. Impact Factor Calculations Cites in 2005 to articles published in: 2004 =118 Number of articles published in: 2004 =123 2003 =134 2003 = 69 Sum:252 Sum:192 Calculation:Cites to recent articles 2521.312 Number of recent articles 192

6. Process ● The citation data are obtained from Institute for Scientific Information (ISI) in Philadelphia, USA ● The results are published as the Science Citation Index (SCI) – Journal Impact Factor – Annual citation rate of a scientific author or research group

7. Problems associated with the use of journal impact factors ● Journal impact factors are not statistically representative of individual journal articles ● Journal impact factors correlate poorly with actual citations of individual articles

8. Is the journal impact factor really representative of the individual journal articles?

9. Copyright ©1997 BMJ Publishing Group Ltd. Seglen, P. O BMJ 1997;314:497 Fig 1 Citation rates in 1986 or 1987 of articles published in three biochemical journals in 1983 or 1984, respectively

10. Copyright ©1997 BMJ Publishing Group Ltd. Seglen, P. O BMJ 1997;314:497 Fig 2 Cumulative contribution of articles with different citation rates (beginning with most cited 5%) to total journal impact. Values are mean (SE) of journals in fig 1; dotted lines indicate contributions of 15% and 50% most cited articles

11. Copyright ©1997 BMJ Publishing Group Ltd. Seglen, P. O BMJ 1997;314:497 Fig 3 Correlation between article citation rate and journal impact for four authors

12. ‘Citable’ items ● Not all published items are counted ● Research papers and short reports are defined as ‘citable’ ● excluding editorials, reviews, or letters

13. Flawed computations ● no correction for self citations  editorials, lively correspondences, review articles, long articles (30-40% inflation) ● the use of an extremely short term index  short publication lags, online-first articles (press articles) ● Basic sciences and dynamic research field e.g. biology, biochemistry VS. Ecology, mathematics

14. Limitation of the database (ISI) ● Books are not included in the database as a source for citations ● Non English journals ● American journals – the mean journal impact of American science was 30% above the world average

15. Journal impact factors and research field Journal19861987 Annual Review of Biochemistry31.635.1 Annual Review of Immunology26.525.2 Annual Review of Cell Biology14.122.8 Annual Review of Genetics14.014.3 Annual Review of Neuroscience15.413.7 Annual Review of Pharmacology10.19.9 Annual Review of Physiology7.89.1 Annual Review of Biophysics7.27.7 Annual Review of Microbiology4.96.4

16. Field correction factors e.g. the article’s citation rate/the impact factor of the journal

17. Is the impact of an article increased by publication in a high impact journal? ● ‘Free ride’ hypothesis : the publication in a high impact journal will enhance the impact of an article ● Two groups of scientific authors – A (x2 in means citation rate) vs.B (x1) – A & B  similar journal preference  A(x2):B

18. Are there alternatives? ● Papers: the mean number of citations each year for 5 or 10 years ● Journals: the rankings based on 1, 7 or 15 years ● The half life ● Frequency of download (e-journals) ● Journal Immediacy Index ● Cited Half-Life Calculations

19. Breakdown of the citations to the journal by the cumulative percent of 2005 cites to articles published in the following years: Cited Half-Life: 5.2 years Cited Year 2005200420032002200120001999199819971996 1995-all # Cites from 2005 41 118 134 93 114 69 111 54 38 39 212 Cumulati ve % 4.01 15.54 28.64 37.7348.88 55.62 66.47 71.75 75.46 79.28 100

20. Back to the basic ● Research  Readers  Users  Population (Patients)

21. Back to the basic ● Research  Readers  Users  Population (Patients) research citations

22. Back to the basic ● Other factors might influence the submission

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