Bibliometrics
In evaluations of research quality and impact, quantitative or so-called bibliometric measures are used. Based on research publications, various measurements can be made, but they are primarily based on citations of published research articles. The measurement results are used, for example, in comparisons or as a basis for appointments and resource allocation.
For some disciplines, mainly within the natural sciences, engineering sciences, and medicine, data from one or a few citation databases are used; the more publications that cite a given publication, the higher the score – ranking – it receives. In the humanities, there are often other publishing traditions, which affect the possibilities for how the research is measured.
Citation-based ranking
There are different forms of calculations to measure citations, and the commercial database providers offer various indicators to measure citations.an be measured.
An individual author or journal can be assigned an H-index score. The H-index score is calculated based on relevant data in each separate database, which means that a researcher’s or journal’s H-index score will vary depending on what data are available in the respective database.
A researcher’s H-index is n if he/she has written at least n publications that have been cited at least n times each. For example, a researcher who has published 24 articles, of which 10 have been cited 10 times or more, has an H-index score of 10.
Clarivate Analytics, the owners of Web of Science, publishes Journal Citation Reports (JCR), which can be used to check a journal’s Impact Factor. Impact Factor is a measurement of the average number of times a journal’s articles have been cited during a certain period of time. Impact Factor is used exclusively for journals indexed in Web of Science. A certain journal’s Impact Factor is based on the number of citing articles indexed in Web of Science.
A specific article in a journal may thus have been cited more or fewer times than the journal's Impact Factor suggests – the measure is an average.
Elsevier has developed a couple of indicators, Source Normalized Impact per Paper (SNIP) and SCImago Journal Rank (SJR), for their database Scopus. These can also be used for analyses of data in other databases than Scopus.
However, in order for these indicators to be of use, a significant part of a discipline’s publications must be indexed in the same database. You can compare journals in Scopus under Compare Sources.
Google Scholar offers statistics of the number of times an author or journal has been cited. However, the quality of the citations data may vary.
