The impact factor is one of the most popular scientometric indicators used for journal performance evaluation. The company «Scientific Publications» suggests defining the features of this metric, its advantages and disadvantages.
How is the impact factor calculated?
This metric was first introduced back in 1955 in a fundamental work by Eugene Garfield in the journal «Science». Traditionally, the impact factor ranking is applied to publications of the Web of Science scientometric database.
The impact factor is calculated as the ratio of the number of citations to the number of articles published in a given period. The calculation of the impact factor is usually based on a two-year period.
For example, to calculate the impact factor of a journal for 2021, the number of articles and their citations for the previous two years, 2020 and 2019, is considered. The citation window will therefore be one year (2021) and the publication window will be two years (2020-2019).
Additionally, there are five-year, «immediacy» (1 year) and ten-year impact factors. Such variations are suggested by the specific nature of the research area. After all, for some sciences, a publication window of two years is a very short period (for example, for the humanities and social sciences).
Journal Citation Reports provides information on calculations of the Journal Impact Factor for the review period. Information on the impact index for the previous year is published each July. That is, the Journal Citation Reports for 2021 will be published in July 2022.
How do I find the Impact Factor?
The impact factor is not assigned to all Web of Science scientometric database journals, but only by those that are included in the Web of Science Core Collection and indexed in Science Citation Index Expanded (SCIE) or Social Sciences Citation Index (SSCI).
Journals of The Emerging Sources Citation Index (ESCI) and Arts & humanity Citation Index (a&HCI) which are part of the Web of Science Core Collection are not assigned an impact factor. This is explained by the specific nature of scientific articles published by journals in these areas (for A&HCI). Journals indexed in the ESCI do not receive impact factors due to the insufficient number of ratings required to calculate this indicator.
To find out which specific journals have an impact factor in the Web of Science database, a special search filter is used.
Detailed information and statistics on the impact factor are available for viewing by click-through: View profile page - Journal Impact Factor.
Advantages and disadvantages of the impact factor
Disadvantages of the impact factor metric:
- It is not a universal indicator. The same impact factor value can be very high for one research area and low for another. For this reason, a quartile index is used to further rank scientific publications.
- It does not cover all publications of the database, so the Journal Citation Indicator was recently introduced as an additional marker.
- The time interval by which the impact factor is calculated is sometimes insufficient for an objective and thorough evaluation of a journal.
- A citation rate, along with the number of publications, is not an exhaustive criterion for determining the quality of publications.
Advantages of the impact factor:
- It is a convenient and comprehensible metric for evaluating the scientific activity of a publication.
- It covers a large number of journals – more than 8,000 publications from 60 countries of the world.
Impact factor analogues
Today, the scientometric world is developing analogues of the impact factor and its modifications. However, scientists should be aware of the fact that only the above-described version is considered classic and is an official development of the Web of Science.
The use of other «impact factors» may indicate scientific dishonesty of publications or databases.
If you need assistance in publishing a scientific article, including publications in the international scientometric databases Scopus and Web of Science, the specialists at "Scientific Publications" will be happy to advise you! Submit an application on the website or contact us in any way convenient for you, and our specialists will respond to your request within one business day.
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