Posted by: bluesyemre | May 23, 2017

#Citation Performance Indicators (A very short introduction) by Phil Davis


Ratio-based indicators

Impact Factor: Total citations in a given year to all papers published in the past 2 years divided by the total number of articles and reviews published in the past 2 years. PROS: Simple formula with historical data. CONS: 2-year publication window is too short for most journals; numerator includes citations to papers not counted in denominator. PRODUCER: Clarivate (formerly Thomson Reuters), published annually in June.

Impact Factor (5-yr): 5-year publication window instead of 2. PROS: Preferred metric in fields in which citation lifecycle is long, e.g., social sciences. PRODUCER: Clarivate, published annually in June.

CiteScore: Total citations in a given year to all documents published in past 3 years divided by the total number documents published in the past 3 years. PROS: Transparency (does not attempt to classify and limit by article type); based on broader Scopus dataset; free resource. CONS: Biased against journals that publish front matter (editorials, news, letters, etc.). PRODUCER: Elsevier, based on Scopus data, updated monthly.

Impact per Publication (IPP): Similar to Impact Factor with notable differences: 3-yr. publication window instead of 2; includes only citations to papers classified as article, conference paper, or review; based on broader Scopus dataset. PROS: Longer observation window; citations are limited to those documents counted in the denominator. CONS: Like the Impact Factor, defining correct article type can be problematic. PRODUCER: CWTS, Leiden University based on Scopus data, published each June.

Source-Normalized Impact per Paper (SNIP): Similar to IPP but citations scores are normalized to account for differences between scientific fields, where field is determined by the set of papers citing that journal. PROS: Can compare journal performance across fields. CONS: Normalization makes the indicator less transparent. PRODUCER: CWTS, Leiden University for Elsevier, published each June.

Portfolio-based indicators

h-index: A measure of the quantity and performance of an individual author. An author with an index of h will have published h papers, each of which has been cited at least h times. PROS: Measures career performance; not influenced by outliers (highly cited papers). CONS: Field-dependent; ignores author order; increases with author age and productivity; sensitive to self-citation and gaming, especially in Google Scholar. PRODUCER: First described by Hirsch, many sources calculate h-index values for individual authors.

h-5: A variation of the h-index that is limited to articles published in the last 5 years. Used by Google Scholar to compare journal performance. PROS: Enables newer journals to be compared with older journals. CONS: h-5 is biased toward larger titles. Google Scholar also reports h5-median, which is intended to address size bias. PRODUCER: Google Scholar. Published annually in June.

Network-based indicators

Eigenfactor: Measures the influence of a journal on an entire citation network. Calculation of scores is based on eigenvector centrality, computed through iterative weighting, such that citations from one journal have more influence than another. PROS: Offers a metric that more closely reflects scientific influence as a construct. CONS: Computationally complex, not easily replicable, and provides the same result for most journals as more simple methods (e.g. Impact Factor). PRODUCER: Clarivate (formerly Thomson Reuters), published annually in June.

SCImago Journal Rank (SJR): Like Eigenfactor but computed upon the Scopus database. PRODUCER: SCImago for Elsevier, published annually in June. A detailed explanation and comparison of Eigenfactor and SJR is found here.

Relative Citation Ratio (RCR): A field-normalized citation metric for articles based on NIH’s PubMed database. A field is defined by the references in the articles co-cited with the paper of interest. For example, if Article A is co-cited by Articles B, C, and D, then Article A’s field is defined by the references contained within Articles B, C, and D. PROS: Allows each article to be defined by its own citation network rather than relying on external field classification. CONS: Sensitive to interdisciplinary citations and multidisciplinary journals. The RCR is dependent upon the Impact Factor for weighting journals listed in references. PRODUCER: NIH.

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