Content Factor: A Measure of a Journal's Contribution to Knowledge
Impact Factor, the pre-eminent performance metric for medical journals, has been criticized for failing to capture the true impact of articles; for favoring methodology papers; for being unduly influenced by statistical outliers; and for examining a period of time too short to capture an articleâs long-term importance. Also, in the era of search engines, where readers need not skim through journals to find information, Impact Factorâs emphasis on citation efficiency may be misplaced. A better metric would consider the total number of citations to all papers published by the journal (not just the recent ones), and would not be decremented by the total number of papers published. We propose a metric embodying these principles, âContent Factorâ, and examine its performance among leading medical and orthopaedic surgery journals. To remedy Impact Factorâs emphasis on recent citations, Content Factor considers the total number of citations, regardless of the year in which the cited paper was published. To correct for Impact Factorâs emphasis on efficiency, no denominator is employed. Content Factor is thus the total number of citations in a given year to all of the papers previously published in the journal. We found that Content Factor and Impact Factor are poorly correlated. We further surveyed 75 experienced orthopaedic authors and measured their perceptions of the âimportanceâ of various orthopaedic surgery journals. The correlation between the importance score and the Impact Factor was only 0.08; the correlation between the importance score and Content Factor was 0.56. Accordingly, Content Factor better reflects a journalâs âimportanceâ. In sum, while Content Factor cannot be defended as the lone metric of merit, to the extent that performance data informs journal evaluations, Content Factorâ an easily obtained and intuitively appealing metric of the journalâs knowledge contribution, not subject to gamingâ can be a useful adjunct.