The scientific community is governed by the "publish-or perish" principle. Therefore, academics are forced to publish their work as often as possible in renowned (peer-reviewed) journals in order to advance their careers. Quite often decisions about research funding are based on bibliometrical criteria (e.g. citation analysis).

Citation analysis is a method for measuring research quality, enabling you to determine how frequently a particular author has been cited in articles or to compare and evaluate journals based on citation counts. Thus one can identify reputable scientists, evaluate journal status, or, by analyzing the connection between a research institution, researcher, subject area, and publication, identify previous and current research emphasis. It is important, however, to always consider several factors to ensure a comprehensive analysis.

The following information is designed to give you a general overview of the most popular bibliometric measures and provide tips on how use these citation tools.

h-index

J.E. Hirsch’s h-index serves as a measure of a researcher’s scientific productivity and impact. This index is often referred to as a “personal  impact factor”. The h-index is a system which ranks all of a researcher’s publications by how often they have been cited. Hirsch defines the h-index as follows: "A scientist has index h if h of his or her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each".

It is important to keep in mind that the h-index is only useful in comparing scientists working within the same field since citation conventions differ substantially between subject disciplines:  e.g. the publication productivity is higher in the life sciences than in the social sciences.

The database Web of Science (WoS) offers an automatic h-index calculator. Please keep in mind, though, that the Web of Science’s h-index is based only on the articles indexed in their database. Therefore, the h-index can strongly vary between vendors.

For the most optimal calculation of your h-index, you can set up your own personal profile at ResearcherID, which you can then use to link unassigned publications in Web of Science to your profile. 

More information is available in these quick guides:

• Quick-Guide Web of Science
• Quick-Guide ResearcherID

Impact Factor

The impact factor (IF), which is also called the journal impact factor (JIF), is an indicator used to rank and compare journals: the higher the impact factor of a journal, the more prestigious it is. Thus publishing in a journal with a high impact factor increases the likelihood of career advancement.

The relevance of the impact factor is, however, controversial, because it serves as a measure of citation frequency but does not reflect the accurate importance of a journal. Self-citations and publications of lesser importance, such as meetings or editorials, are included in the impact factor calculation, but books are excluded, which can lead to distorted results.

To determine and evaluate the impact factor, you can consult Web of Science’s JCR impact factor listings:

• Journal Citation Reports (JCR)
• Journal Citation Reports (JCR) Tutorial