Impact & Discovery

Journal and Article Relevancy Measures

There are numerous ways of measuring the performance and/or impact of a journal or article, generally based on an analysis of citations. Below, we've listed some resources for definitions and further information on a few of the metrics used to rank articles and journals. 

Journal Level Metrics

SciMago Journal Rank  (SJR) is "the measure of journal’s impact, influence, or prestige"; expresses average number of weighted citations in a particular year to articles published in a journal in the previous 3 years (citations from more important or prestigious journals are given more weight). Data are from the Scopus database (owned by Elsevier)

Source Normalized Impact per Paper (SNIP) measures contextual citation impact by weighting citations based on the total number of citations in a subject field. Also based on Scopus database.

Relative Price Index is the price per article, price per citation.

Days to First Decision is the number of days from submission to peer review first decision. 

Rejection Rate is the number of rejections divided by the number of submissions in a given journal.

Google Scholar Metrics (based on the Google Scholar database)  uses the h-index, h-core, and h-median of articles that were published in the last 5 complete calendar years. The definitions of h-index, h-core and h-median are found here. 
Each year, Thomson Reuters issues the
 Journal Citation Report (JCR), which measures a few things, including:  

  • Article Influence Score - a measure of the average influence of each article in a journal over the first 5 years following publication -- it’s similar to the 5-year impact factor (see below) in that it's “a ratio of a journal’s citation influence to the size of the journal’s article contribution over a period of 5 years”. Mean score is 1.00; >1.00 indicates that each article has above-average influence, <1.00 indicates that each article has below-average influence.
  • Eigenfactor Score - an estimate of percentage of time library users spend with the journal (it uses an algorithm based on number of times articles published in the journal in the past 5 years were cited in a particular year, but also which journals contributed these citations; highly cited journals influence the network more than less cited journals). The information is based on the Web of Science database (owned by Thomson Reuters)
  • Impact Factor - the "impact factor" of a journal is a measure reflecting the average number of citations to recent articles published in the journal.
    • 2-year impact factor: The average number of citations received per paper published in that journal during the 2 preceding years.
    • 5-year impact factor: Similar in nature to the 2-year Impact Factor, but instead of counting citations in a given year to the previous 2 years and dividing by source items in these years, citations are counted in a given year to the previous 5 years and again divided by the source items published in the previous 5 years.
Some clarification about “citation”: 
  • Total cites = Total number of citations to the journal in a year (citations to papers published in any year).
  • Citable items = Usually articles, reviews, proceedings, or notes published in a journal; not editorials or letters to the editor
  • Cited half-life = Median age of journal items cited in a particular year (i.e., half of the citations to the journal are to items published within the cited half-life)

Immediacy index is the number of citations the articles in a journal receive in a given year divided by the number of articles published (indicates how quickly articles in a journal are cited). 

Article Level Metrics / Alternative Metrics

Further information about alternative metrics that may be of interest .