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Research Publishing & Impact: Journal Metrics

About Journal Metrics

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.

Use Journal metric terms, Key measurement tools and Journal ranking.

Journal metric terms

Journal Impact Factor (JIF or IF) - from Journal Citation Reports (JCR), an Incites database from Clarivate Analytics, formerly Thomson Reuters.

= 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.

2016 JCR data was made available from 14 June 2017.

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CiteScore and SNIP are found using Scopus - Compare sources or Scopus Journal Metrics

  • CiteScore calculates the average number of citations received in a calendar year by all items published in that journal in the preceding three years. Do not compare CiteScores across subject fields.

              2016 CiteScore data was made available from 2 June 2017

  • SNIP (Source Normalized Impact per Paper) measures contextual citation impact by weighting citations based on the total number of citations in a subject field. SNIP is the ratio of a source's average citation count per paper, and the 'citation potential' of its subject field. It aims to allow direct comparison of sources in different subject fields.

Note: The SNIP may change for current and previous years when extra journal content is added to Scopus.

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h-index

The journal h-index measures a journal’s impact based on the number of citations to it.

The h-index is the number of papers (N) with at least N citations each. For example, a journal with an h-index of 9 has at least nine published papers, each of which has been cited at least nine times.

Two key factors may impact on a journal h-index:

1. The journals indexed by the database - journals not indexed by the database will not be included in the h-index; no database indexes every journal. Search by journal title, including subtitles, and journal abbreviations.

2. The date range over which the journal history h-index is being measured.

Web of Science and Scopus are the main source databases for h-index information for journals used by scientists.

Publish or Perish - merge this data with that from Web of Science and Scopus, then deduplicate results

The h-index is not widely used outside the Sciences. At Otago, Humanities scholars are advised not to use the h-index. Citation counts do not necessarily reflect research impact in the Humanities. Social Science scholars may find the journal h-index useful when selecting where to publish.

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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.

Note: The SJR may change for current and previous years when extra journal content is added to Scopus.

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Field Weighted Citation Impact (FWCI) shows how well cited an article is, when compared to similar articles. This impact is  irrespective of subject area, publication year or output type. FWCI takes into account the differences in research behaviour across disciplines. It is particularly valuable for cross-disciplinary research. Citations received up to 3 complete calendar years after publication are considered (p.55-57).

  

If the FWCI = 1, the output performs just as expected for the global average; if the FWCI = 1.48, it means 48% more cited than expected.

Find the FWCI using Scopus at article level; and SciVal (updated weekly from Scopus data) at author, institution and regional level.

Learn more:   SciVal Metrics Guidebook - see p61-65

 

Category Normalised Citation Impact (CNCI) uses the actual count of citing items, divided by the expected citation rate for documents with the same document type, year of publication and subject area. When a document is assigned to more than one subject area an average of the ratios of the actual to expected citations is used.

   

If the CNCI = 1, this represents performance at par with world average. A CNCI value of 2 is considered twice world average.

Find the CNCI and JNCI (Journal Normalised Citation Impact) using Incites, from Clarivate Analytics, formerly Thomson Reuters. This metric is useful for benchmarking at author, institutional or regional level.

Learn more:   Incites Indicators Handbook - see p11-12

 

Complementary Indicators - consider using:

  • FWCI by Subject area/s
  • Outputs in top citation percentiles
  • Publications in top journal percentiles
  • International collaboration
  • % of Articles in the top 1% (or 10%) of journals
  • Documents in Q1 indicators (# or %)
  • Highly cited papers or Hot papers

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.  

  • Intended to reflect the influence and prestige of journals.  
  • Considers which journals have contributed to these citations so that highly cited journals, and those with lots of articles, will influence the network more than lesser cited, or smaller journals.
  • References from one article in a journal to another article from the same journal are removed, so that Eigenfactor Scores are not influenced by journal self-citation. 
  • Like the Journal Impact Factor but with weighting for high cites. Metrics are currently available up to JCR 2014 data.

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.

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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.

  • Measures the average influence, per article, of the papers published in a journal.  
  • Roughly comparable to the 5-Year Journal Impact Factor; available in Incites JCR search results
  • Determines the average influence of a journal’s articles over the first five years after publication =               

Learn more:        

See Citation Metrics: Alternative Metrics as it applies to journals.

Limitations

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:

  • Journals with review articles have higher impact factors (more people read and cite these).
  • Impact factors can be biased estimates because non-articles increase a journal’s impact factor, e.g. letter to the editor.
  • Wide variations between different research fields inherent to the different patterns of publication in those fields.
  • Differences in journal metric terms used by different companies, e.g. Journal Impact Factor v. CiteScore.
  • Scopus indexes nearly twice as many journals as Web of Science so some metrics will differ, e.g. journal h-index.
  • Different subject categories of journals are used so comparison of ranking metrics is fraught.
  • A journal’s impact factor is no indication of how heavily a specific article within has been used.
  • Increased metrics when a journal publishes more issues per year, and more articles in one issue.
  • Higher impact journals tend to have higher retraction frequencies [source]
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Key measurement tools

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SciVal (Elsevier) offers quick, easy access to the research performance of 5,500 research institutions and 220 countries worldwide. SciVal enables you to navigate the world of research and devise an optimal plan to drive and analyse your performance.

Contact your Subject Librarian for access to SciVal with Otago researcher names already set up.

View the SciVal Online Manual

 

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  • Comprehensive coverage for journals in the sciences and medical sciences
  • Primarily English-language, North American journals
  • Excludes Journal self citations
  • Useful for disciplines with a longer timeframe for citations to be generated.

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