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Editor's Notes |
The publishers and editorial boards of professional journals are keenly interested in quality of content as well as overall reputation and prestige. Defining and measuring the quality and value of a professional journal, however, can be an elusive, complex undertaking—almost as challenging as evaluating the quality of health care.
The traditional method of evaluating a journal's quality and prestige is the impact factor (IF). As a researcher and as a former academic dean who had to make decisions about the quality of faculty scholarship, I have often compared the IFs of different journals. Although I always appreciated that larger values are "better," I must confess that I never gave much thought to the meaning of an IF.
In September, I represented Physical Therapy at the Fifth International Congress on Peer Review and Biomedical Publication, organized by JAMA and the BMJ Publishing Group. I had the privilege of hearing a keynote talk by Dr Eugene Garfield, the originator of the IF. He created this ratio in the 1960s as the first quantitative means of evaluating, ranking, and comparing professional journals.1 Today, it is used globally as the gold standard. What does an IF really tell us?
The IF is a simple yet elegant measurement that is based on the frequency with which a journal's substantive articles are cited in the scientific literature. To generate the IF for a particular journal (Physical Therapy) in a given year (2004), we calculate the ratio of the number of citations to any items published in that journal in the previous 2 years (201) relative to the total number of substantive articles published in the journal during that same 2-year period (103). By dividing the 201 citations by the 103 articles, we arrive at an impact factor of 1.95. We can interpret the meaning of an IF for a particular journal by comparing it to the IFs of other journals that are placed in the same category by Journal Citation Reports (JCR).
So, how good is an IF of 1.95? Physical Therapy's impact factor currently is #2 among the top 25 rehabilitation journals published in the world as ranked by JCR, surpassed only by the Journal of Electromyography and Kinesiology in the #1 position (IF=2.1). In 2003 and 2002, Physical Therapy was ranked #1 among all 20 rehabilitation journals, and its IF has improved consistently over the past 7 years, from 1.192 in 1998 to its current value of just under 2.0.
Physical Therapy's quality among the top rehabilitation journals is impressive! This achievement reflects not only the growing quality of research and scholarship relevant to physical therapy, but also the hard work of the Editorial Board and staff who work with authors. Furthermore, it is an indicator of the Journal's past success in attracting to its pages the very best scholarship being written in the world today. Physical Therapy publishes content that is of high value and use to the rehabilitation research community, as shown by the community's citations of this work within their own publications. The Journal's high IF also reflects the overall prestige enjoyed by Physical Therapy worldwide and helps explain why approximately half of all manuscripts submitted to Physical Therapy come from researchers working outside the United States. Our Journal has become an international resource to the physical therapy profession, and this is an accomplishment that should make us all proud.
I have come to appreciate the competitive aspect of journal editing as I have attended various professional meetings over the past year. Journal editors love to compare IFs. On numerous occasions, other rehabilitation journal editors have asked about Physical Therapy's IF. Many react with surprise when I explain our IF rankings, and some openly ponder why we are ranked higher than all of the other major rehabilitation journals. It reminds me of how baseball fans invariably debate the statistics that reveal a baseball player's value to his team: batting averages versus on base percentages versus slugging percentages.... No one statistic tells the whole story, but each number reveals something about the quality of the player. So, too, with professional journals.
Our IF reflects positively on the quality of what is published in Physical Therapy, but it does not tell the full story of this Journal's value to its readership. The use of IF as an indicator of quality rests on the assumption that citation frequency accurately represents a journal's importance to its end users. The validity of this assumption can legitimately be questioned for a journal like ours, where the end users include not only researchers who write manuscripts for publication, but clinicians—most of whom do not publish in the peer-reviewed literature. Clinician readers who do not publish do not have a chance to "vote" on the quality and prestige of a particular journal through a statistic like IF. So, although there is some evidence that IF is a reasonable indicator of quality as judged by a general clinical medicine audience,2 citation frequency is more directly associated with the quality and value of clinical journals to researchers than to clinicians.
How can a journal like Physical Therapy assess its quality and usefulness for its clinical audience? Circulation is one indicator of quality; we can examine whether it is growing and expanding worldwide. Circulation is limited as a marker of success, however, because journal subscriptions often are included with membership in professional societies.
Marketing surveys are another common indicator of quality and perceived importance. In a recent APTA readership survey,3 for example, 89% of the more than 1,200 member respondents reported "reading/looking through" Physical Therapy during the previous 6 months, and 44% reported that they would read Physical Therapy first if the Journal and 5 other physical therapy publications arrived on their desk at the same time. A full 65% reported saving the entire issue of Physical Therapy for future reference, while 61% reported "reading/looking through" 3 of the 4 previous issues of the Journal. The results of this survey would seem to indicate that Physical Therapy is read regularly and valued to a high degree among responding APTA members. Unfortunately, market survey response rates are notoriously low, so we can't be certain that the respondents represent the larger Journal readership.
When I look at the "available evidence," I conclude that Physical Therapy as a professional, scientific journal is on the right track. Under the leadership of the late Jules Rothstein, the Journal took important strides to attain the high degree of quality and respect that it has today. The future challenge is to not become complacent. In the coming years, under new editorial leadership, Physical Therapy will need to build on its strong foundation and aggressively move forward to achieve its vision of being the premier international journal for physical therapy research and scholarship. Only in this way can the Journal meet the needs of its worldwide audience.
During the past year, I have had the distinct honor and privilege to serve as Acting Editor in Chief of Physical Therapy. I have enjoyed working with authors to help them disseminate their important work, and I have come to appreciate more than ever the superior talent and devotion of this Journal's Editorial Board, managing editor, and professional staff. They are essential elements to Physical Therapy's achievements in quality, and all of us are indebted to this remarkable group of colleagues for their dedication and service to our profession. I look forward to working with the Journal's new editor in chief in the years ahead.
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