The database Web of Science, owned by Clarivate Analytics, is considered among many within the research community as the foremost quality based database of peer-reviewed journal articles. It is also an important analytical tool to analyze international research communication based on how the journal articles in the database cite each other. Web of Science is also used when bibliometric citation analyses are made on a national level, for example for distributing research funds.

One of the most well-known products of the database is the journal indicator the Impact Factor (IF), or Journal Impact Factor (JIF). This indicator intends to measure the impact a journal has based on the number of citations its articles have received. The idea is that the more citations a journal receives the greater its impact is on the research community within its specific discipline.

JIF and other journal indicators are found in the database Journal Citation Reports (JCR) in which you can also identify journals within different subject categories and compare them based on these indicators.

We will present JCR and offer short descriptions about the most common indicators in the database:

Journal Citation Reports (JCR)

JCR is solely based on citations from journal articles, conference papers and books and book chapters indexed in Web of Science. You need to create an account to be able to choose more indicators (Customize Indicators). It is mainly the two first indicators (Journal Impact Factor and 5 Year Impact Factor) that are most commonly used within the research community and in research evaluation. 

• Journal Impact Factor (JIF)
  JIF is defined as all citations to a journal from one specific JCR year (for example, 2016) to articles published in that journal the two preceding years (2014 and 2015 in our example). This number is divided with the total number of citable articles (research articles and review articles) published in the journal the two preceding years (2014 and 2015).
  
  JIF works as an approximation of the average citation score per citable article in a journal. A JIF of 1.0 means that the articles published in the journal the two preceding years, on average, have been cited one time. A JIF of 2.5 means that the articles published in the journal the two preceding years, on average, have been cited two and a half times.
   
• 5 Year Impact Factor
  The 5-year IF works in the same way as the JIF but instead you count the citations for the five preceding years. This indicator is commonly used within some areas, such as the social sciences, psychology, and mathematics since within these areas it usually takes longer time for articles to be cited.
• Eigenfactor Score
  Eigenfactor Score is based on the number of times articles in a journal published the latest five years have been cited based on a particular JCR year (for example, 2016). The indicator considers from which journals the citations come so that citations from journals that themselves are highly cited are weighted higher than those that come from a journal that is cited less. Citations from the same journal are not taken into account which means that the Eigenfactor Score is not affected by a journal's self-citations. The Eigenfactor Score intends to consider the different citation cultures of different scientific disciplines.
• Article Influence Score
  Article Influence Score is calculated by dividing the Eigenfactor Score (see above) with the number of articles in the journal from the same five-year period. Article Influence Score measures the average impact per article in the journal. The average value is 1.00. A value above 1.00 means that the articles of the journal, on average, have an impact above average. A value below 1.00 means that the articles of the journal, on average, have an impact below average.

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