JOURNALS DIRECTORY>> Journal Impact Factor
Eugene Garfield, founder of the Institute for Scientific Information, devised the impact factor in the 1950s. Impact factors are calculated each year by Thomson Scientific for the journals it indexes, and the factors are published in Journal Citation Reports.  View the JCR page for JMPT (November 19, 2010).

What is impact factor? According to Clarivate Accelerating innovation: “A Journal Citation Reports subscription gives you a systematic, objective means to evaluate the world’s leading scientific and scholarly journals. By analyzing citation references, Journal Citation Reports measures research influence and impact at the journal and category levels, and shows the relationship between citing and cited journals.”  The Clarivate Analytics Impact Factor “This essay was originally published in the Current Contents print editions June 20, 1994, when Clarivate Analytics was known as The Institute for Scientific Information® (ISI®).”

Opinions vary as to the value of impact factors as measures of a journal’s value. Below is a selection of Open Access articles from peer reviewed journals, listed by date [earliest first]. Run a PubMed search on  journal impact factor ; free full text. This page updated March 4, 2019.

• Garfield E. Citation indexes for science. A new dimension in documentation through association of ideas. 1955.  [Reprinted in:] Int J Epidemiol 2006 Oct;35(5):1123-7; discussion 1127-8.  [First published in: Science 1955;122:108–11.]
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  Smith R. Commentary: The power of the unrelenting impact factor–Is it a force for good or harm? Int J Epidemiol 2006 Oct;35(5):1129-30.
  Porta M, Fernandez E, Bolúmar F. Commentary: The ‘bibliographic impact factor’ and the still uncharted sociology of epidemiology. Int J Epidemiol 2006 Oct;35(5):1130-5.
• Lokker C, Haynes RB, Chu R, McKibbon KA, Wilczynski NL, Walter SD. How well are journal and clinical article characteristics associated with the journal impact factor? A retrospective cohort study. J Med Libr Assoc 2012 Jan;100(1):28-33.  PubMed Record
• Wu XF, Fu Q, Rousseau R.  On indexing in the Web of Science and predicting journal impact factor. J Zhejiang Univ Sci B 2008 Jul;9(7):582-90.   PubMed Record
• The impact factor game. It is time to find a better way to assess the scientific literature PLoS Med 2006 Jun;3(6):e291.
• Chew M, Villanueva EV, Van Der Weyden MB.  Life and times of the impact factor: Retrospective analysis of trends for seven medical journals (1994-2005) and their Editors’ views. J R Soc Med 2007 Mar;100(3):142-50.
• Oh HC, Lim JF. Is the journal impact factor a valid indicator of scientific value? Singapore Med J 2009 Aug;50(8):749-51.  PubMed Record
• Grzybowski A. The journal impact factor: How to interpret its true value and importance. Med Sci Monit 2009 Feb;15(2):SR1-4. [Full text available for download]  PubMed Record
• Mathur VP, Sharma A. Impact factor and other standardized measures of journal citation: A perspective. Indian J Dent Res 2009 Jan-Mar;20(1):81-5.  PubMed Record
• Brunarski DJ. Impact of the chiropractic literature; references,citations and the research “impact factor”. Dynamic Chiropractic Canada 2010; 3(5): 6 p.
• van der Wall EE. Journal impact factor: holy grail? Neth Heart J 2012 Oct;20(10):385-6. PubMed Record
• Abbas AM. Bounds and inequalities relating h-index, g-index, e-index and generalized impact factor: An improvement over existing models. PLoS One 2012;7(4):e33699.  PubMed Record
• Ramin S, Sarraf Shirazi A. Comparison between Impact factor, SCImago journal rank indicator and Eigenfactor score of nuclear medicine journals. Nucl Med Rev Cent East Eur2012 Aug 27;15(2):132-6. PubMed Record
• Björk BC, Solomon D. Open access versus subscription journals: a comparison of scientific impact. BMC Med 2012 Jul 17;10:73. doi: 10.1186/1741-7015-10-73. PubMed Record
• Bernstein J, Gray CF. Content Factor: A measure of a journal’s contribution to knowledge. PLoS One 2012;7(7):e41554. PubMed Record
• Lundh A, Barbateskovic M, Hróbjartsson A, Gøtzsche PC. Conflicts of interest at medical journals: the influence of industry-supported randomised trials on journal impact factors and revenue – cohort study. PLoS Med 2010 Oct 26;7(10):e1000354.  PubMed Record
• Froud R, Bjørkli T, Bright P, Rajendran D, Buchbinder R, Underwood M, Evans D, Eldridge S. The effect of journal impact factor, reporting conflicts, and reporting funding sources, on standardized effect sizes in back pain trials: A systematic review and meta-regression. BMC Musculoskelet Disord. 2015 Nov 30;16:370. PubMed Record
• Azer SA, Holen A, Wilson I, Skokauskas N. Impact factor of medical education journals and recently developed indices: Can any of them support academic promotion criteria? J Postgrad Med. 2016 Jan-Mar;62(1):32-9. PubMed Record
• Paulus FM, Rademacher L, Schäfer TA, Müller-Pinzler L, Krach S. Journal impact factor shapes scientists’ reward signal in the prospect of publication. PLoS One. 2015 Nov 10;10(11):e0142537. PubMed Record
• Liu XL, Gai SS, Zhou J. Journal impact factor: Do the numerator and denominator need correction? PLoS One. 2016 Mar 15;11(3):e0151414. PubMed Record