Definition: The journal impact factor measures the importance of a journal by calculating the times its articles are cited.
How Impact Factor is Calculated: The calculation is based on a two-year period and involves dividing the number of times articles that were cited by the number of articles that are citable.
Experts stress that there are limitations in using impact factors to evaluate a scholar's work. There are many reasons cited for not relying on impact factor alone to evaluate the output of a particular individual. Among these are the following:
- A single factor is not sufficient for evaluating of an author's work.
- Journal values are meaningless unless compared within the same discipline. Impact factors vary among disciplines.
- The impact factor was originally devised to show the impact of a specific journal, not a specific scholar. The quality and impact of the author's work may extend beyond the impact of a particular journal.
According to Jim Testa, a researcher for ThomsonReuters Scientific, the most widespread misuse of the Impact Factor is to evaluate the work of an individual author (instead of a journal). "To say that because a researcher is publishing in a certain journal, he or she is more influential or deserves more credit is not necessarily true. There are many other variables to consider." (interview 6/26/2008 in Thomson Reuters blog entry)
Thanks to Linda Shackle and Lydia LaFaro of Arizona State University for sharing their citation guide information! This guide includes content adapted with their permission.
To use Journal Citation Reports, follow the steps below:
- Open Journal Citation Reports.
- Select either the Science or Social Sciences Edition and the Year.
- Select an option to search for a specific journal, or to view a group of journals.
- To search for a specific journal, you may search by Full or Abbreviated journal title, title word, or ISSN.
- Click on the journal title to see Journal Information, Impact Factor, Immediacy Index, Cited Half-Life, Cited Journal Graph,etc.
For more information about Journal Citation Reports, you can:
- click on the Information for New Users located in the upper right hand corner of the database opening page;
- view the Journal Citation Reports tutorial created by Thomson ISI;
- or view the Use JCR Wisely page.
Alternative journal ranking sources
A free and searchable database, Eigenfactor covers the natural and social sciences and "also lists newsprint, PhD theses, popular magazines and more." The Eigenfactor is now included in Journal Citation Reports. It continues to be listed here for use on its own.
The website includes an interactive mapping function that shows the relationship of branches of science to each other based on the size of the field and the citations generated by the journals of the field. Rather than the "soft" categories used in Journal Citation Reports, where a journal may be located in one or more categories, Eigenfactor uses a hard category where a journal can only fit in one discipline.
Google Scholar Metrics
Ranks publications in Google Scholar by analyzing the last five years of journal articles from websites that follow Google's inclusion guidelines as well as conference articles and preprints from a small number of manually identified sources. Excludes publications with less than 100 articles during the five-year period and those with no citations. The metrics provided are the h-index, h-core, h-median, h5-index, h5-core, and h5-median.
Harzing.com - Journal Quality List
Compiles rankings of journals from various sources in the areas of Economics, Finance, Accounting, Management, and Marketing.
Humanities Journal Rankings
European Science Foundation's subgroup for the Humanities. Scroll down to see a table that contains links to journal rankings in the Humanities.
This source ranks journals that are indexed by ISI's Science Citation Index. The website allows you to customize your ranking and is interactive.
Source Normalized Impact per Paper (SNIP)
Based on Scopus data, SNIP is a European ranking that attempts to address the problems of varying citation rates among disciplines and the lack of statistics to indicate levels of significant differences.
SCImago Journal & Country Rank (SJR)
A free source that uses data from Elsevier's Scopus database. Includes a "compare" feature that compares journal citation among countries. There is also a "map generator" that shows citation relationships by country. The SJR indicator aims to measure "the current 'average prestige per paper'" of research journals and is one of a new set of journal rangings based on eigenvector centrality (Gonzalez-Pereira 2009) .