Some journals are read and cited more than others. Measuring the impact of a journal may help authors identify where to publish as well as how much visibility their research may expect in return. It is important to note that journal impact measures vary among research disciplines due to differing citation behavior and thus cannot be directly compared.
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Journal Impact Factor
A journal’s Impact Factor averages the number of recent citations to the journal by the number of articles it recently published. The 2009 Impact Factor is calculated by taking the number of citations made in 2009 to articles published in the journal in 2007 and 2008, and dividing by the total number of that journal's 2007 and 2008 articles. Therefore the Impact Factor of a journal only considers a brief period and can change from year to year. Impact Factor can be viewed in either of ISI’s two data sources:
- Web of Knowledge: Search by journal title. In an article record, click Journal Citation Reports towards the bottom of the record, under "Journal Information."
- Journal Citation Reports: Compare journals in a subject discipline: view a journal’s Impact Factor with others in its discipline.
SCImago Journal Rank (SJR)
The SJR is a free website based on the citation data tracked in Elsevier’s Scopus database. The ranking system works like the Google PageRank algorithm as it incorporates citation data as well as relationships among journals (via citations).
- Search for a journal’s rank by title in SCImago’s “Journals Search”.
- List journals by subject using the SCImago “Journal Rankings”.
A journal’s Eigenfactor Score counts the citations made to a journal over time, but gives more weight to the citations from highly ranked journals than weaker ones, another use of PageRank theory. Therefore Eigenfactor ranks the overall impact of a journal, and not the impact of articles within that journal.
- Eigenfactor.org Journal Ranking reports a journal’s Eigenfactor Score, a measure comparable to a journal’s Impact Factor, and Article Influence.
- ISI Journal Citation Reports also lists Eigenfactor Score and Article Influence.
Impact Per Publication
A journal's Impact Per Publication (IPP) is the total number of citations in a year to articles published in the three previous years, divided by the total number of articles published in those three years. 2013 IPP would be calculated by taking the number of citations in 2013 to articles published between 2010 and 2012, then dividing that by the total number of articles published between 2010 and 2012. IPP is limited to only scholarly articles, conference papers and review articles and does not consider citations from trade publications, newspapers, or books. The IPP is similar to the Impact Factor but uses Scopus rather than Web of Science to gather its data and three years rather than two as the publication period.
- Look up a journal's IPP and compare IPPs between journals using Scopus's Journal Analyzer Tool.
SCImago Journal Rank calculates a journal’s h-index, or the number of articles in a journal (h) that have received at least h citations.
"Why the Impact Factor of Journals Should not be Used for Evaluating Research" by P. O. Seglen (1997) in the British Medical Journal.
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