
Advantages and disadvantages of using impact factors
Advantages include:
- Accepting that they must be used carefully and that citation patterns are specific to particular areas of research, impact factors can be a useful tool when trying to find an objective measure of quality.
- Impact factors are calculated from the number of citations received by the papers published in a named journal during the previous two years. In this way, they can reflect the changing status of a journal within a research field, as the number of citations increases or declines.
Disadvantages include:
- Impact factors should not be used as a standard of comparison between disciplines. Citation practice depends very much on the subject area, with the result that a high impact factor for one discipline may look extremely low in comparison with another. Look at the following examples from the Journal Citation Reports, for impact factors for 2006:
Biology: the top 5 journals in the subject group, arranged by impact factor
PLoS Biology |
14.101 |
FASEB Journal |
6.721 |
Bioessays |
5.965 |
Quarterly Review of Biology |
5.944 |
Biological Reviews |
5.565 |
Medicine: the top 5 journals in the subject group, arranged by impact factor
New England Journal of Medicine |
51.296 |
Lancet |
25.800 |
JAMA - Journal of the American Medical Association |
23.175 |
Annals of Internal Medicine |
14.780 |
PLoS Medicine |
13.750 |
Critics point out that impact factors are calculated as an average for the total published output of a journal and that this information should not be used to gauge the importance of an individual research paper. A small number of papers published in a journal may have received a large proportion of the citations.