Bibliometric indicators

The evaluation of research and development in the Czech Republic and the evaluation of authors in the international context uses various existing indicators to measure the success and prestige of journals, authors, teams of authors, institutions, etc.

There are a number of bibliometric indicators. Selected indicators that you may encounter most often are described below and also briefly in this presentation (.ppt, Czech only).

Comparison of the methodology for calculating the key indicators

The article "A new approach to the metric of journals’ scientific prestige: The SJR indicator" provides a brief comparison of the calculation of the most commonly used indicators – the SJR, AIS and the IF. 

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The most commonly used bibliometric indicators

AIS (Article Influence Score)

The AIS is a metric for journals designed to estimate the importance of a journal regardless of its size (number of articles published). It is an indicator based on the value of the Eigenfactor. In essence, it indicates the average number of citations per article over a 5-year period. It roughly corresponds to the 5-year impact factor, except that the citations received are weighted according to several criteria within the Eigenfactor indicator. This is one hundredth of the Eigenfactor divided by the ratio of the number of articles in the journal to the total number of articles in WoS over the period. Thus, the number and quality (i.e., citation rate) of articles is the main factor that influences the value of AIS.

AIS is one of the two basic bibliometric indicators according to the current  Methodology 2017+. It has the advantage of omitting self-citations (it does not count citations of the journal itself), distinguishing the importance of the scientific journals from which the citations come, and taking into account longer citation periods (it expresses the degree of average influence of each journal article over the five years following its publication).

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It is an indicator of the citation rate of scientific journals included in the Scopus database. It is the average number of citations a journal receives over a three-year period. Its calculation is based on the same principle as the impact factor. The CiteScore is equal to the number of citations in the current year to articles published in the previous three years. CiteScore is calculated once a year, always in the summer of the following year, i.e., CiteScore 2018 was calculated and published in approximately June 2019.

CiteScore has 23,830+ titles from the Scopus database, including peer-reviewed journals, scientific journals, book series and conference proceedings, in 330 disciplines. CiteScore covers 12,000+ more titles than the Impact Factor. CiteScore has the advantage of being accessible even without a subscription to the Scopus database through the Scopus Sources page and allows anyone to check the value of CiteScore by clicking into the numerator (citations) and denominator (documents). In addition, the CiteScore Tracker can be used to track the current evolution of the CiteScore value. This allows you to track the development of the value month by month in the current year.

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The Eigenfactor shows the total citations of articles published over the past 5 years in the current year. It shows the citation rate of a journal regardless of the number of articles published. The average citation rate with respect to the number of articles in the journal is then expressed by the Article Influence Score.

The Eigenfactor is the percentage of success rate of a journal among all journals in the Journal Citation Report. The sum of all Eigenfactor values is equal to 100. Compared to the impact factor, the Eigenfactor attempts to eliminate some of the negatives of just a basic count of citations received. In addition to the five-year period, the prestige of the journal from which the citation comes is also reflected in the Eigenfactor calculation (citations from more prestigious - more cited - journals are weighted more heavily than citations from less prestigious journals). Like AIS, it does not count self-citations.

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The Hirsch index (h-index) is an indicator that can be used to track the citation response of one author or a group of authors. It indicates how many articles by a given author (group of authors) have a higher number of citations than the serial number of the article in the list of his/her articles, ordered in ascending order of citation count.

The H-index of the author can be calculated from the citation responses of his/her published articles. The H-index is equal to the serial number of the most recent publication (publications are listed in descending order of the number of citations received) that has a number of citations equal to or greater than its serial number. The H-index is the number h, which indicates the number of publications that have been cited at least h times.

Example I.
1.      article A ... 10 citations
2.      article B ... 5 citations
3.      article C ... 3 citations ... h-index =3 => order = number of citations
Regardless of the total number of publications, 3 publications were cited at least 3 times.

Example II.
1.      article A ... 79 citations
2.      article B ... 62 citations
3.      article C ... 14 citations... h-index = 3
4.      article D ... 2 citations
Regardless of the total number of publications and citations received, 3 publications were cited at least 3 times.

Similar to the Impact Factor, the Hirsch Index does not compare the performance of authors in different fields. It is discipline-specific and results are difficult to compare across disciplines. A carefully maintained personal bibliography, including citation references, is an essential prerequisite for a complete and high-quality basis for the h-index.

More information:

Hirsch J. E. (2005): An index to quantify an individual's scientific research output. Proc. Natl. Acad. Sci. 102:16569-16572.
Batista P. D. et al. (2005): Is it possible to compare researchers with different scientific interests?
Editorial: The Hirsch Index and measuring the quality of scientific papers. Ulster Med J 2008, 77 (1).
The h Index for Computer Science.

Impact factor

A scientometric indicator for the journal impact factor expressing the citation rate of articles published in a given journal in the previous two years. It is calculated only for journals included in Journal Citation Reports. It is always calculated for a calendar year (total number of citations of the journal in the last two years / total number of articles of the journal in the last two years) in the summer of the following year, i.e., IF 2017 will be calculated and published in approximately June 2018.

You can find the impact factor via the Journal Citation Reports by entering the ISSN or journal name. 

Scimago Journal Rank (SJR)

Scimago Journal Rank is based on data for the Scopus database. Its principle is very similar to the AIS indicator, but it is calculated on the basis of 3 years of data. The first stage of the calculation calculates the so-called "total prestige of the journal", which depends on the total number of articles and the number of citations it receives (citations are weighted according to the prestige of the citing source). This phase is roughly similar to the calculation of the Eigenfactor. In the second stage of the calculation, the SJR is calculated as the ratio of the total prestige of the journal to the number of articles in the journal. Unlike AIS, the Eigenfactor counts self-citations up to a maximum rate of 33%. The calculation works with the prestige of the journal from which the citation originates (citations from more prestigious - more cited - journals have a higher weight than citations from a less prestigious journal).

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SNIP (Source Normalized Impact per Paper)

SNIP is a value that takes into account the number of citations in each field. 

The SNIP citation indicator is the work of Henk F. Moed from the University of Leiden, the Netherlands. This indicator assesses the citation data of a journal by scientific discipline. SNIP works with sub-components RIP (Raw Impact per Paper), which is very similar to the impact factor, and RDCP (Relative Database Citation Potential). The latter, which is very complicated to calculate, represents the citation potential of a journal, derived according to the citation practices of the field. 

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