Impact Factor

Impact Factor (IF) is a measure reflecting the average number of citations to articles published in scientific journals, books, or conference proceedings. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones.

Overview

The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information (ISI). Impact factors are calculated yearly starting from 1975 for journals listed in the Journal Citation Reports (JCR).

Calculation

The impact factor for a journal is calculated based on a two-year period. It can be viewed as the average number of times published papers are cited up to two years after publication. For example, the 2023 impact factor of a journal would be calculated as follows:

IF_2023 = (Citations in 2023 to articles published in 2021-2022) / (Number of articles published in 2021-2022)

This formula gives a ratio between citations and recent citable items published. Thus, the impact factor of a journal is a measure of the frequency with which the "average article" in a journal has been cited in a particular year or period.

Uses and Criticisms

The impact factor is used to compare different journals within a certain field. Higher impact factors are often seen as a symbol of prestige. Universities, grant committees, and tenure panels often use it as a proxy for the quality of a journal when evaluating the performance of researchers.

However, the impact factor has received widespread criticism. Critics argue that the impact factor:

• Encourages gaming the system through practices such as citation manipulation and strategic citation.
• Favors large fields over small ones.
• Can be influenced by publishing review articles or original research articles, which tend to get more citations than other types of articles.
• Does not measure the quality of content but rather the visibility and popularity of the journal.

Alternatives and Supplements

Due to the limitations of the impact factor, several alternatives and supplements have been proposed:

• h-index: A measure that evaluates both the productivity and citation impact of the publications of a scientist or scholar.
• SCImago Journal Rank (SJR): A measure that considers both the number of citations received and the importance of the journals where such citations come from.
• Eigenfactor: A rating scale for journals that considers the number of times articles from the journal published in the past five years have been cited in the JCR year.

See Also

• Bibliometrics
• Scientometrics
• Citation analysis