Journal impact or ranking is based on the number of citations articles receive, signifying a journal's importance and influence. Impact factors and rankings are not comparable across disciplines or databases. Impact metrics are not available for all journals. Keep a track by measuring impact with different tools.
Journal impact measures are often used in the field of science, medicine, technology, business and social science but are not a valuable measure of quality for arts and humanities journals.
Journal impact or ranking metrics are by their nature controversial. As with all measures of scholarly impact, they should be used in the appropriate context, and not in isolation.
New and emerging journals, including open access titles, may not have had time to appear on ranking or other lists.
= average number of times an article, from a journal published in the last 2 years, has been cited in the JCR year.
This well known journal metric uses citation data from the Web of Science Core Collection. The 5-year Impact factor is also available. Compare sources within a subject category, e.g. Psychology.
Researchers are often encouraged to publish in, and read, journals with high impact factors, to enhance their research profile and awareness.
Scopus - Compare sources uses two journal metric terms:
Publish or Perish - merge this data with that from Web of Science and Scopus, then deduplicate results
SCImago Journal Rank (SJR) demonstrates journal rankings or prestige, based on Scopus data. SJR normalises for differences in citation behaviour between different subjects. Subject field, quality, and reputation of the journal have a direct effect on the value of a citation.
= average number of citations per document by total journal citations within a 3-year period, in a subject category, while assigning higher value to citations from more prestigious journals.
Eigenfactor Score (EF) - a measure of a journal's importance to the scientific community, based on past 5 years' data from Journal Citation Reports (JCR). A journal's Scores are scaled so that the sum of all journal scores is 100. In 2014, PLOS One had the highest EF Score of 1.533.
Normalised Eigenfactor Score (EFn) - scaled so that the journal’s mean score = 1.00 . A journal with a Normalized Eigenfactor Score of 3 has three times the total influence of the average journal in the JCR. In 2014, PLOS One had the highest EFn Score of 171.7.
Article Influence Score: The mean Article Influence Score is 1.00. An Article Influence Score greater than 1.00 indicates that the articles in a journal have an above-average influence.
See Citation Metrics: Alternative Metrics as it applies to journals.
Obvious factors can heavily influence journal impact factors, such as journal title changes, or publishers gaming the system by requiring authors to cite articles from other journals by the same publisher. However there are more systematic problems: