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 5.012, which means that on average, each of its 2004 and 2005 articles was cited 5.012 times in 2006.
How to find the Journal Impact Factor by individual journal title or by subject groupings:
Individual journal title:
1. Go to JCR (opens a new window).
2. Select a JCR edition year from the drop menu.
3. Click radio button to the left of ‘Search for a specific journal.’
4. Click Submit button.
5. Enter journal information by complete title, ISSN, abbreviated title, or title word.
6. Click Search button.
Subject:
1. Go to JCR (opens a new window).
2. Select a JCR edition year from drop menu (leave view group of journals by subject category).
3. Click Submit button.
4. Select one or more subject categories (hold down <Ctrl> key to select multiple categories).
5. Select Journal or Category data sorts. Under View Journal Data, select Impact Factor.
6. Click Submit button.
In results table click individual journal title for complete information (e.g., explanations of impact factor, immediacy index, citing and cited half-life).
Eigenfactor
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 eigenfactor.org (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.
h-index
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.
“A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np – h) papers have no more than h citations each.” [For details in calculation, see Hirsch 2005.] An h-index of 16 means, for example, that a researcher has published 16 papers that each has been cited at least 16 times. Therefore, the h-index reflects both the number of articles as well as the number of citations per article.
How to find the h-index of an individual author in Web of Science:
1. Go to Web of Science (opens in a new window).
2. Enter author’s name and be sure the pull-down box indicates Author.
3. Click Search.
4. Refine Results by subject areas or other criteria if desired.
5. Click ‘Create Citation Report’ link (right side of window, just above results list).
6. The Citation Report lists the h-index to the right of the graphs (Note: click blue [?] link for more information).
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. Click 'Cited Reference Search' at the top of the page.
3. Enter the name of the primary 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 Factors
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. Available at http://dx.doi.org/10.1002/asi.20936
Cham J. (2008). Your (real) impact factor. PhD Comics. Originally published December 8, 2008. Available at http://www.phdcomics.com/comics.php?f=1108
Dong P, Loh M, Mondry A. (2005). The “impact factor” revisited. Biomedical Digital Libraries, 2:7. Available at http://dx.doi.org/10.1186/1742-5581-2-7
Garfield E. (1996). How can impact factors be improved? BMJ, 313(7054):411-413. Available at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2351785&tool=pmcentrez
Garfield E. (2003). The meaning of the Impact Factor. International Journal of Clinical and Health Psychology, 3(2):363-369. Available at http://www.garfield.library.upenn.edu/papers/meaningofif2003.pdf
Garfield E. (2006). The history and meaning of the journal impact factor. JAMA, 295(1):90-93. Available at http://jama.ama-assn.org/cgi/content/full/295/1/90
h-index. (2009). In Wikipedia, The Free Encyclopedia. Retrieved January 13, 2009. Available at http://en.wikipedia.org/wiki/H-index
Hirsch JE. (2005). An index to quantify an individual’s scientific research output. PNAS, 102(46):16569-16572. Available at http://dx.doi.org/10.1073/pnas.0507655102
IF article from Thomson Reuters http://thomsonreuters.com/products_services/science/free/essays/impact_factor/
Impact Factor. (2009). In Wikipedia, The Free Encyclopedia. Retrieved January 13, 2009. Available at http://en.wikipedia.org/wiki/Impact_factor
Jeang K-T. (2007). Impact factor, H index, peer comparisons, and Retrovirology: Is it time to individualize citation metrics? Retrovirology, 4:42. Available at http://dx.doi.org/10.1186/1742-4690-4-42
Monastersky R. (2005), October 14. The number that’s devouring science. The Chronicle of Higher Education, 52(8):A12. Available at http://chronicle.com/weekly/v52/i08/08a01201.htm
Rossner M, Van Epps H, Hill E. (2007). Show me the data. The Journal of Cell Biology, 179(6):1091-1092. Available at http://dx.doi.org/10.1083/jcb.200711140
Rovner SL. (2008). The import of impact: New types of journal metrics grow more influential in the scientific community. Chemical & Engineering News, 86(20):39-42. Available at http://pubs.acs.org/cen/science/86/8621sci1.html
Simons K. (2008). The misused impact factor. Science, 322(5899):165. Available at http://dx.doi.org/10.1126/science.1165316