The journal impact factor is a measure of the frequency with which the "average article" in a journal has been cited in a particular year. It is calculated by dividing the number of current citations to articles published in the two previous years by the total number of articles published in the two previous years. The impact factor will help you evaluate a journal’s relative importance, especially when you compare it to others in the same field. An Impact Factor of 1.0 means that, on average, the articles published one or two year ago have been cited one time. An Impact Factor of 2.5 means that, on average, the articles published one or two year ago have been cited two and a half times. Citing articles may be from the same journal; most citing articles are from different journals. Journal impact factors are searchable with Journal Citation Reports® through ISI Web of Knowledge (requires a subscription, University of Utah has access through the Marriot Library). Follow the link for more information on the impact factor.
Journal Citation ReportsThe Journal Citation Reports (JCR) database is a unique and comprehensive tool providing bibliometric analysis of more than 5,900 journals in the areas of science and technology and of 1,700 journals in the social sciences. Coverage is international and includes journals published by over 3,300 publishers in 60 countries.
The aim of the JCR is to provide a systematic and objective means of determining the relative importance of science and social sciences journals within their subject categories. Information for each title includes the "impact factor" (a measurement of the frequency with which the average article has been cited in a particular year) and the "immediacy index" (how quickly the average article in a journal is cited). The JCR can show you the highest-impact journal, most frequently used journals, hottest journal, and largest journals. JCR uses Thomson Reuters (ISI Web of Knowledge) citation data(requires a subscription, the University of Utah has access through the Marriot Library).
The Eigenfactor Score measures the number of times articles from the journal published in the past five years have been cited in the JCR year. Like the Impact Factor, the Eigenfactor Score is essentially a ratio of the number of citations to the total number of articles. However, unlike the Impact Factor, the Eigenfactor Score:
- Counts citations to journals in both the sciences and social sciences.
- Eliminates self-citations. Every reference from one article in a journal to another article from the same journal is discounted.
- Weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal.
Eigenfactor scores are scaled so that the sum of the Eigenfactor scores of all journals listed in Thomson's Journal Citation Reports (JCR) is 100. In 2006, the journal Nature has the highest Eigenfactor score, with a score of 1.992. The top thousand journals, as ranked by Eigenfactor score, all have Eigenfactor scores above 0.01.
The Article Influence Score calculates measures the relative importance of the journal on a per-article basis. It is the journal's Eigenfactor Score divided by the fraction of articles published by the journal. That fraction is normalized so that the sum total of articles from all journals is 1. The mean Article Influence Score is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence. In 2006, the top journal by Article Influence score is Annual Reviews of Immunology, with an article influence of 27.454. This means that the average article in that journal has twenty seven times the influence of the mean journal in the JCR. Article Influence uses Thomson Reuters (ISI Web of Knowledge) citation data.
The SCImago Journal & Country Rank (SJR) is a publicly available portal that includes the journals and country scientific indicators developed from the information contained in the Scopus® database (Elsevier B.V.). These indicators can be used to assess and analyze scientific domains. Journals can be compared or analyzed separately. Country rankings may also be compared or analyzed separately. Journals can be grouped by subject area (27 major thematic areas), subject category (313 specific subject categories) or by country. Citation data is drawn from over 34,100 titles from more than 5,000 international publishers and country performance metrics from 239 countries worldwide. Is a prestige metric based on the idea that ‘all citations are not created equal’. With SJR, the subject field, quality and reputation of the journal has a direct effect on the value of a citation.
- Is weighted by the prestige of the journal, thereby ‘leveling the playing field’ among journals
- Eliminates manipulation: raise the SJR ranking by being published in more reputable journals
- ‘Shares’ a journal’s prestige equally over the total number of citations in that journal
- Normalizes for differences in citation behavior between subject fields
SJR portal is free for users.
Bibliometrics and more information @ University of Utah, Marriott Library Guides
Ten Rules in Using Publication and Citation Analysis (Bibliometrics)
WHITE PAPER Using Bibliometrics in Evaluating Research by David A. Pendlebury, Research Department, Thomson Reuters, Philadelphia, PA USA