Introduction

Journal Impact Factor (JIF) shows the average number of times articles from a journal published in the past two years that have been cited in the JCR year. This is how Journal IF of 2019 is calculated:

Calculation of Journal Impact Factor in the Year 2019:

 IF in 2019  = No. of citations received in 2019 from all items published in 2017 and 2018 / No. of articles & reviews published in 2017 and 2018

e.g.

• Impact Factor of 1.0 means that, on average, the articles published one or two years ago have been cited one time.
• Impact Factor of 2.5 means that, on average, the articles published one or two years ago have been cited two and a half times.

The calculation is based on citations, hence publications in journals with higher IF may have higher chance of being cited as compared to publications published in journals with relatively lower IF.

► Note:

• Citation practices vary between disciplines, so Journal Impact Factors should NOT be used to compare journals across different subject areas.
• Journal Impact Factors cannot assess the quality of individual articles.
• Journal Impact Factor (JIF) is available to all Web of Science Core Collection journals, including those indexed in Science Citation Index Expanded (SCIE), Social Sciences Citation Index (SSCI), Arts and Humanities Citation Index (AHCI) and Emerging Sources Citation Index (ESCI).

The Journal Citation Indicator (JCI) is the average Category Normalized Citation Impact (CNCI) of citable items (articles & reviews) published by a journal over a recent three year period. The average JCI in a category is 1. Journals with a JCI of 1.5 have 50% more citation impact than the average in that category. It may be used alongside other metrics to help you evaluate journals.

For example:

JCI = 1.5 ►The average JCI in a category is 1. Journals with a JCI of 1.5 have 50% more citation impact than the average in that category.

► Note:

• All journals covered in Journal Citation Reports (JCR) have JCI displayed in the profile.
• The JCI is a normalized indicator and is not category dependent, journals in multiple categories will have a single JCI. The average JCI of any category is approximately 1.

The 5-year Impact Factor is the average number of times articles from a journal published in the last five years have been cited in the JCR year (as compared to the last 2 years for IF).

Calculation of 5-Year Impact Factor in the Year 2019:

5-Year IF in 2019  = No. of citations to all items published in 2014-2018 / No. of articles & reviews published in 2014-2018

Advantage of 5-year Impact Factor

The calculation of the 5-year Impact Factor includes a longer time span which allows more citation activities. It may be more appropriate for subject disciplines such as Arts and Humanities which take longer time to have the citation activities.

Eigenfactor Score:

• measures the number of times articles from the journal published in the past five years have been cited in the JCR year.
• considers the "importance" of incoming citations, with citations from highly cited journals have more influence than those from lesser cited journals.
• with Eigenfactor Scores, references from one article in a journal to another article from the same journal are removed (journal self-citation is excluded).

Article Influence Score:

• determines the average influence of journal's articles over the first five years after publication.
• is calculated by multiplying the Eigenfactor Score by 0.01 and dividing by the number of articles (recorded in the Journal Citation Reports) in the journal, normalized as a fraction of all articles in all publications.
• is roughly analogous to the 5-Year Journal Impact Factor in that it is a ratio of a journal’s citation influence to the size of the journal’s article contribution over a period of five years. 

The mean of Article Influence Score for each article is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence.

Advantage of  Eigenfactor Score and Article Influence Score

They allow comparison across subject disciplines.

Scholarly references join journals together in a vast network of citations. The Eigenfactor score and the Article Influence score are calculated by the structure of the entire network (instead of purely local citation information) to evaluate the importance of each journal so it automatically accounts for the differences in citation activities across subject disciplines and allows better comparison across research areas.

They are more suitable for research areas which take longer time to have citation activities.

In many research areas, articles are not frequently cited until several years after publication. The Eigenfactor score and the Article Influence score are calculated based on the citations received over a five year period, thus it may be more applicable to the research areas which take longer time to accumulate citation activities.