An Impact Factor is one measure of the relative importance of a journal, individual publication, or researcher to literature and research.

Journal impact factors, citations to publications, h-index of researchers are used to measure the importance and impact of research.

Informed and careful use of the impact data is essential and the following must be kept in mind:

• The number of times a paper is cited is not a measure of its actual quality.
• Some tools that measure the impact data do not incorporate books.
• Certain disciplines have low numbers of journals and usage. One should compare journals or researchers within the same discipline.
• Review articles are cited more often and can change results.
• Self-citing may skew results.