Journal Impact Factors in Sport and Exercise Science, 1999–2000
Will G Hopkins
Department of Physiology and School of Physical Education, University of Otago, Dunedin 9001, New Zealand. Email.
Sportscience 5(3), sportsci.org/jour/0103/wghimp.htm, 2001 (2164 words)
Reviewed by Frank I Katch, Department of Exercise Science, University of Massachusetts, Amherst Ma 01003
The impact factor of a journal is the number of times its average recent article was cited annually in recent publications. It is a measure of the importance of a journal that researchers should consider when submitting material for publication. I present here an analysis of impact factors of journals in exercise and sport science for the years 1999 and 2000. The uncertainty in the impact factor for journals like Medicine and Science in Sports and Exercise (MSSE, current impact factor of 2.6) is probably less than ±0.2 (95% likely limits). Journals with an impact factor in the range 1.0 to 4.9 in 1999 showed little overall increase in 2000 (mean, 0.1), but wide variation existed between journals (standard deviation of change, 0.5). MSSE's rise of 0.5 since 1999 is therefore well above the average change. Reprint pdf · Reprint doc
KEYWORDS: citation, ISI, MSSE, publication
At the end of each year the Institute for Scientific Information (ISI) publishes its Journal Citation Reports for science and social science journals (ISI, 2001). The most interesting feature of the reports is the journal impact factor, a measure of the importance of each journal. The impact factor for a journal is roughly the number of times per year the average paper in the journal was cited in any recent journal. More precisely, the impact factor for the year 2000 (the current impact factor) is the number of times articles in the journal for the years 1998 and 1999 were cited in ISI-recognized journals published in 2000, divided by the number of articles in the journal in 1998 and 1999. At the ISI website there is a page of detail about this statistic and others for each journal. You can link to these pages only if your institution has a subscription to the Web version of the journal citation reports. Your library may also/instead have a hard copy of the reports.
A researcher building a career in a traditional academic setting should take impact factors into account when submitting material for publication, because publishing in high-impact journals will enhance the researcher's chances of appointment and promotion. A researcher in a more applied setting may have to find other ways to get recognition for productivity, because the often-used case-study qualitative reports and materials that benefit students, clients, and communities usually do not qualify for publication in ISI-recognized journals.
Table 1 summarizes the impact factors for journals of interest to researchers in exercise and sport science. The table includes impact factors for 1999, culled from an article about the impact factor published at this site last year (Hopkins, 2000). Some academics are interested in rank-ordering journals by impact factor, so I have provided the table as an Excel spreadsheet containing columns for various sub-disciplines of exercise and sport science. Download the spreadsheet and sort it by sub-discipline and/or impact factor to make comparison of journals easier. Be aware that discipline-specific original-research journals such as MSSE will never score as highly as the generic high-flyers like Science and Nature or the review journals that overlap with more well-funded disciplines like genetics, molecular biology, medicine, and neuroscience.
Some academics also keep on eye on changes in the impact factor of their favorite journals. In doing so, they should take into account the magnitude of the typical error of measurement of the impact factor, and the mean and typical variation of the change in impact factor of all related journals. In what follows, I demonstrate how to assess the change in impact factor between 1999 and 2000 for MSSE, one of our key journals.
The impact factor refers to a number of citations divided by a number of articles, so the error in the impact factor will depend on these numbers (which are known) and on the correlation between them (which is unknown). The correlation will always be positive and will always reduce the error, so I obtained a conservative estimate of the error by assuming a correlation of zero. The error for MSSE's current impact factor of 2.6 turns out to be less than ±0.1, and the 95% likely limits of the true impact factor are therefore less than ±0.2. I conclude that the improvement from MSSE's value of 2.1 last year is clear cut.
The question then arises as to the magnitude of the change. By analyzing the impact factors for 1999 and 2000 in Table 1 with the reliability spreadsheet at this site, I determined that journals with impact factors between 1.0 and 4.9 in 1998 showed an increase of 0.1 ± 0.5 (mean ± standard deviation). MSSE's increase of 0.5 therefore compares well with other journals on the rise, but it is not exceptional: of the 93 journals with impact factors in the 1.0–4.9 range, 14 had a larger increase than MSSE and 78 had a smaller increase or a decrease.
Hopkins WG (2000). Impact factors of journals in sport and exercise science. Sportscience 4(3), sportsci.org/jour/0003/wgh.html (1592 words)
Institute for Scientific Information (2001). 2000 journal citation reports (science and social science editions). Philadelphia, PA: ISI