Skip to main content

Calculating Impact Factor: How Bibliographical Classification of Journal Items Affects the Impact Factor of Large and Small Journals

Abstract

As bibliographical classification of published journal items affects the denominator in this equation, we investigated how the numerator and denominator of the impact factor (IF) equation were generated for representative journals in two categories of the Journal Citation Reports (JCR). We performed a full text search of the 1st-ranked journal in 2004 JCR category “Medicine, General and Internal” (New England Journal of Medicine, NEJM, IF = 38.570) and 61st-ranked journal (Croatian Medical Journal, CMJ, IF = 0.690), 1st-ranked journal in category “Multidisciplinary Sciences” (Nature, IF = 32.182) and journal with a relative rank of CMJ (Anais da Academia Brasileira de Ciencias, AABC, IF = 0.435). Large journals published more items categorized by Web of Science (WoS) as non-research items (editorial material, letters, news, book reviews, bibliographical items, or corrections): 63% out of total 5,193 items in Nature and 81% out of 3,540 items in NEJM, compared with 31% out of 283 items in CMJ and only 2 (2%) out of 126 items in AABC. Some items classified by WoS as non-original contained original research data (9.5% in Nature, 7.2% in NEJM, 13.7% in CMJ and none in AABC). These items received a significant number of citations: 6.9% of total citations in Nature, 14.7% in NEJM and 18.5% in CMJ. IF decreased for all journals when only items presenting original research and citations to them were used for IF calculation. Regardless of the journal’s size or discipline, publication of non-original research and its classification by the bibliographical database have an effect on both numerator and denominator of the IF equation.

This is a preview of subscription content, access via your institution.

Fig. 1

References

  1. Garfield, E. (2006). The history and meaning of the journal impact factor. JAMA, 295, 90–93.

    Article  Google Scholar 

  2. Seglen, P. O. (1997). Why the impact factor of journals should not be used for evaluating research. BMJ, 314, 498–502.

    Google Scholar 

  3. Joseph, K. S., & Hoey, J. (1999). CMAJ’s impact factor: Room for recalculation. CMAJ, 161, 977–978.

    Google Scholar 

  4. Joseph, K. S. (2003). Quality of impact factors of general medical journals. BMJ, 326, 283.

    Article  Google Scholar 

  5. Adam, D. (2002). The counting house. Nature, 415, 726–729.

    Google Scholar 

  6. The PLoS Medicine Editors (2006). The impact factor game. PLoS Medicine, 3, e291.

    Article  Google Scholar 

  7. Brown, H. (2007). How impact factor changed medical publishing—and science. BMJ, 334, 561–564.

    Article  Google Scholar 

  8. Walter, G., Bloch, S., Hunt, G., & Fisher, K. (2003) Counting on citations: A flawed way to measure quality. MJA, 178, 280–281.

    Google Scholar 

  9. Lundberg, G. D. (2003). The “omnipotent” science citation index impact factor. MJA, 178, 253–254.

    Google Scholar 

  10. Nankivell, B. J., et al. (2003). The natural history of chronic allograft nephropathy. The New England Journal of Medicine, 349, 2326–2233.

    Article  Google Scholar 

  11. Marusic, A., & Marusic, M. (2003). Teaching students how to read and write science: Mandatory course on scientific research and communication in medicine. Academic Medicine, 78, 1235–1239.

    Article  Google Scholar 

  12. Martinson, B. C., Anderson, M. S., & de Vries, R. (2005). Scientists behaving badly. Nature, 435, 737–738.

    Article  Google Scholar 

  13. Williams, G., & Hobbs R. (2007). Should we ditch impact factors? BMJ, 334, 568–569.

    Article  Google Scholar 

  14. Dellavalle, R. P., Schilling, L. M., Rodriguez, M. A., Van de Sompel J., & Bollen J. (2007). Refining dermatology journal impact factors using PageRank. Journal of the American Academy of Dermatology, 57, 116–119.

    Article  Google Scholar 

  15. Thomson Scientific (2005). Journal performance indicators. Available at: http://www.scientific.thomson.com/products/jpi/. Accessibility verified October 19, 2007.

Download references

Acknowledgements

Contributions: AM, MM, and NK conceived and designed the study; MR and RG collected all data, and analyzed them with AM. AM wrote the manuscript and MR, RG, NK and MM revised it for important intellectual content. All authors approved the final version of the manuscript for submission. Funding: This study was supported by the grant from the Ministry of Science, Education and Sports of the Republic of Croatia, No. 108-1080314-0245 to MM. Competing interests: AM and MM are Coeditors in Chief of the Croatian Medical Journal. NK is Book Review Editor fro the Croatian Medical Journal. None of them receives any pay for their work in the journal.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Ana Marusic.

Additional information

Preliminary results of the study were presented at the 2006 ORI Research Conference on Research Integrity, Tampa, FL, December 1–3, 2006.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Golubic, R., Rudes, M., Kovacic, N. et al. Calculating Impact Factor: How Bibliographical Classification of Journal Items Affects the Impact Factor of Large and Small Journals. Sci Eng Ethics 14, 41–49 (2008). https://doi.org/10.1007/s11948-007-9044-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11948-007-9044-3

Keywords

  • Journal
  • Impact factor
  • Bibliographical database
  • Indexing