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Are you familiar with the impact factor?
The impact factor has become a serious consideration in the selection of the journals to which some scientific researchers send manuscripts. This trend is particularly true for our colleagues in Europe and Asia. The higher the impact factor, the more desirable the journal, even if that journal is not published in the researcher's native country, or even in the same region of the world in which the researcher resides and works. By being published in a journal with a high impact factor, despite the fact that that journal is published in a foreign land and in a foreign language and that that journal may not be widely available in the researcher's home country, the researcher is likely to receive more academic credit than he or she would for publishing the same work in the researcher's own national scientific journal. On the surface, this seems incredible.
How, and why, did the impact factor come to assume such a position of prominence and, thereby, become so important to researchers?
The impact factor is a product of the Institute of Scientific Information (ISI) of Philadelphia, PA. ISI was founded in 1958 to create a database listing the content of more than 4,000 scientific journals published worldwide [1]. ISI has no official governmental, scientific, or academic status. ISI is not an eleemosynary, public service corporation. ISI is a completely independent, nongovernmental, private, commercial company. With the database, ISI creates products for sale. If you want information from ISI, you have to buy it. The original purpose of the database was to sell current listings of selected topics in the world's scientific literature to researchers who wanted to stay abreast of scientific developments in their specific areas of interest. Other uses have since been found for the database—among them, the production of the impact factor.
The impact factor was first produced in the early 1960s. As originally envisioned, the impact factor served solely as an internal ISI index of the relative quality of a scientific journal that helped the company decide whether ISI should include that journal in its database.
The impact factor for a specific journal is derived from the frequency of citation in the scientific literature for articles published during the previous 2 years divided by the number of citable articles, as identified in the Institute's database, published in that journal during the same 2 years. The more citations and the fewer articles published, the higher the impact factor.
Some authorities dispute the ISI rankings, and there is plenty of room for argument [2, 3]. The top 25 journals, those with the highest impact factors, include many readily acknowledged elite publications, such as Nature, New England Journal of Medicine, Science, and Lancet. But, curiously, 60% of the supposed top 25 are review journals, journals that publish only reviews and summaries of past research. That is to say, these journals report no fresh research, nothing new [2]! How could that be? How can you have "impact" if you don't publish new research? That's the way it works with the impact factor. It is not a perfect world.
The impact factor has also come to be used for many other purposes, some of which are an extension of the original purpose. Librarians may apply the impact factor as a bibliometric parameter to use in selecting journals to purchase for institutional libraries. Publishers may use the impact factor to monitor and compare the performance of journals and journal editors. Researchers may use it to select journals in which to publish their work.
On the other hand, the impact factor has unfortunately also been adopted for purposes for which it was not originally intended—as a means of evaluating the work of individual researchers [3]. This occurs to a greater extent in Europe than in Asia. The impact factor is used much less frequently in the evaluation of faculty in the United States. In Europe and Asia, medical school deans and administrators have seized the impact factor as objective evidence of the quality and importance of their faculty's publications. It is the practice of some medical schools to use the cumulative impact factor of a faculty member as a determinant of faculty rank, promotion, and salary. Researchers are therefore understandably reluctant to submit articles to journals with a low impact factor. Journals in languages other than English rarely have high impact factors, which puts them at a decided disadvantage in this regard.
In general, articles published in English are easier to access and therefore more likely to be cited. As a consequence, the adoption of the impact factor has created great difficulties for non—English language national medical journals. Many non—English language journals now publish abstracts in English to increase the opportunity for citation. The National Library of Medicine database, MEDLINE (PubMed), is likely to be used by researchers the world over for literature searches related to their studies. Not all of the world's medical journals qualify for inclusion in MEDLINE.
As might be expected, researchers subject to surveillance by their overseeing impact-factor devotees seek out and publish in those journals with the highest impact factor in order to receive the most academic credit. Departmental chairs encourage their faculty to submit research to these journals for the same reason. English language journals, such as the AJR, are the beneficiary of this practice.
The impact factor is also subject to deliberate manipulation. Certain types of articles, such as reviews and technical reports, are more likely to be cited than others, such as case reports and pictorial essays. To increase a journal's impact factor, editors can increase the number of reviews and eliminate case reports and pictorial essays. Editors can allow more references to be included in all articles in the belief that their journals will thereby benefit from more citations. An editor might even suggest or require that a certain number of citations be made to articles previously published in his or her journal, which will then artifically inflate the impact factor of that journal. To support this contention, see the letter to the editor [4] and reply [5] in this issue on this subject.
As can be seen from the foregoing, the impact factor is somewhat of a game, a game that the AJR has decided not to play. Our authors and readers are pretty satisfied with our journal as it is. We are therefore reluctant to tinker with our editorial content for the sole purpose of manipulating the AJR's impact factor.
Below appears a list of journals in the field of radiology for the year 2000 ordered by their impact factors, from highest to lowest (Appendix 1). But because "the ISI will only grant permission for an individual journal to publish their own impact factor, categories, and rankings" and because "data regarding impact factors from other journals may not be published" (personal communication, Schweppenheiser L [Manager, Index Products Production, Journal Citation Reports, ISI]), I can only tell you that during the year 2000, according to ISI, although the AJR published the largest number of "citable" articles and had the second highest number of citations of all journals in Appendix 1, the AJR ranked 21st in impact factor. Maybe that makes sense to you. Peruse the list. Of course, you are free to draw your own conclusions.
APPENDIX 1: Journal Rankings Sorted by Impact Factor from Journal Citation Reports: 2000 Science Edition [6] Filtered by the Category of "Radiology, Nuclear Medicine & Medical Imaging"
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