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Impact Factors

Journal Impact Factor
Journal Impact Factor is frequently used as a proxy for the importance of a journal to its field. Below are tools for finding the impact of a journal or group of journals.

Journal Citation Reports (JCR)
The JCR provides quantitative tools for ranking, evaluating, categorizing, and comparing journals. The impact factor is one of these; it is a measure of the frequency with which the “average article” in a journal has been cited in a particular year or period. Journal impact factors apply only to a journal or group of journals, but not to individual articles or researchers.

The impact factor of a journal in a particular year is the number of citations received in the current year to articles published in the two preceding years divided by the number of articles published in the same two years. For example, Pediatrics has a 2006 impact factor of 5.196, which means that on average, each of its 2013 and 2014 articles was cited 5.196 times in 2015.

Impact Factor - in Web of Science InCites:
 - Journal Citation Reports (Journal Titles Ranked By Impact Factor) 
 - Essential Science Indicators (Top Papers By Research Field)

Eigenfactor ranks and maps scientific knowledge:

  • Ranks journals similar to Google ranking of websites. It uses the structure of the entire network (instead of purely local information) to evaluate the importance of each journal.
  • Measures journal price as well as citation influence. The Cost-Effectiveness Search orders journals by a measure of the value of the dollar they provide.
  • Ranks scholarly journals as well as newspapers, theses, popular magazines, etc.
  • Adjusts for citation differences across disciplines, allowing for better comparison across research areas.
  • Calculations are based on the citations received over a 5-year period vs. 2 years in JCR.
  • Available free of charge on the web, and also in JCR beginning with the 2007 edition.

How to find the Eigenfactor:
1. Go to (opens a new window).
2. Search for a single journal name or choose a subject category.
3. Select a year.
4. Click Search.

Note: Cost effective (searches by category) and advanced search (searches by Thomson JCR subject categories, publisher and other fields) are also available.


Author Impact Factor
The author impact factor calculates the scientific value of a given researcher or author. You can try the h-index or compile cited references using Web of Science.

The h-index quantifies the actual scientific productivity and the apparent impact of the scientist. The h-index is based on the author’s most cited papers and the number of citations they have received from other articles.

 See this page for more information on the h-index, and the handout (PDF) with step-by-step instructions.

Web of Science Cited Reference Search

Cited references make it possible to find other documents that are related by topic or subject to the original document. Cited references (reference that cite an individual article) may be used to measure the usage and impact of a cited work. Note that cited references can be influenced by author self-citing or publishing in an open access journal.

Citation analysis, which involves counting how many times a paper or research is cited, assumes that influential scientists and important works are cited more often than others.

Cited Reference Search is one of the features in the Web of Science (WoS) database. The number in the Citing Articles column in WoS indicates the number of times the reference has been cited in all years of WoS, regardless of how many years you are searching. Note that Citing Article reference may not include all the known citations of the paper, just those in journals covered by WoS.

How to perform a Cited Reference Search:
1. Go to Web of Science (opens in a new window).
2. Use the dropdown arrow next to Basic Search to change it to Cited Reference Search.
3. Enter the Cited Author and the Cited Year or a limited range of years, then click Search.
4. If you retrieve too many hits, return to the form and add the abbreviated title of a Cited Work.
5. After you click Search, you will see references from the citation index that contain the cited author/cited work data you entered. You can note how many times the article or work has been cited in the Citing Articles column.
6. Select references by checking the box to the left of each reference you want.
7. To retrieve these citing articles, click Finish Search. You have now retrieved the records of articles that cite the author/reference you selected (Note: if the citing article is a published proceedings, these will not return, as Carpenter Library does not subscribe to the two proceedings citations indexes in WoS).
8. Clicking on 'Analyze Results' (right side of window, just above results list) allows you to view rankings of the authors, journals, etc. for you set of results.

Adapted from the University of Washington Health Sciences Libraries’ HealthLinks How-To: Impact Factor


Further Reading About Impact Factors 

Althouse BM, West JD, Bergstrom CT, Bergstrom T. (2008). Differences
in impact factor across fields and over time
. Journal of the American Society for Information Science and Technology, 60(1):27-34. doi: 10.1002/asi.20936 

Ball P., (2005) Index aims for fair ranking of scientists. Nature
18;436(7053):900. PMID: 16107806

Bornmann L, Marx W, Gasparyan AY, Kitas GD. (2012) Diversity, value
and limitations of the journal impact factor and alternative metrics.
 Rheumatol Int. 32(7):1861-7. doi: 10.1007/s00296-011-2276-1. PMID: 22193219

Burke D, Phillips LH 2nd. (2012) Is the "impact factor" a valid measure of the impact of research published in Clinical Neurophysiology and Muscle &
 Muscle Nerve. 46(3):309-12. doi: 10.1002/mus.23608. PMID: 22907220 

Dong P, Loh M, Mondry A. (2005). The "impact factor" revisited. Biomedical Digital Libraries, 2:7. doi:10.1186/1742-5581-2-7

Garfield E. (2006). The history and meaning of the journal impact factor. JAMA, 295(1):90-93. doi:10.1001/jama.295.1.90. PMID: 16391221

h-index. (2016). In Wikipedia, The Free Encyclopedia. Retrieved September 21, 2016. Available at

Hirsch JE. (2005). An index to quantify an individual's scientific research
 PNAS, 102(46):16569-16572. doi: 10.1073/pnas.0507655102

Impact Factor. (2009). In Wikipedia, The Free Encyclopedia.
Retrieved January 13, 2009. Available at

Johnson MH, Cohen J, Grudzinskas G. (2012) The uses and
abuses of bibliometrics
 Reprod Biomed May;24(5):485-6. doi: 10.1016/j.rbmo.2012.03.007. PMID: 22578381

Kulkarni AV, Aziz B, Shams I, Busse JW. (2009) Comparisons of
citations in Web of Science, Scopus, and Google Scholar for articles published in general medical journals.
 JAMA 302(10):1092-6. doi:
10.1001/jama.2009.1307. PMID: 19738094

McVeigh ME, Mann SJ.(2009) The journal impact factor denominator: defining citable (counted) items. JAMA 302(10):1107-9. doi:
10.1001/jama.2009.1301. PMID: 19738096 Erratum in: JAMA. 2009 Nov 11;302(18):1972.

Nahata MC. (2009) Journal impact factor: what it is and is not. Ann
43(1):112-3. doi: 10.1345/aph.1L635. PMID: 19126821

Rossner M, Van Epps H, Hill E. (2007). Show me the data. The Journal of
Cell Biology
, 179(6):1091-1092. doi: 10.1083/jcb.200711140

Stidham RW, Sauder K, Higgins PD. (2012) Using bibliometrics to advance your academic career. Gastroenterology. 143(3):520-3. doi: 10.1053/j.gastro.2012.07.024. PMID: 22828355


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