Department of Orthopedic Surgery, Veterans Hospital, Philadelphia, Pennsylvania, United States of America.
PLoS One. 2012;7(7):e41554. doi: 10.1371/journal.pone.0041554. Epub 2012 Jul 23.
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 article's long-term importance. Also, in the era of search engines, where readers need not skim through journals to find information, Impact Factor's 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, "Content Factor", and examine its performance among leading medical and orthopaedic surgery journals. To remedy Impact Factor's 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 Factor's 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 "importance" 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 journal's "importance". In sum, while Content Factor cannot be defended as the lone metric of merit, to the extent that performance data informs journal evaluations, Content Factor--an easily obtained and intuitively appealing metric of the journal's knowledge contribution, not subject to gaming--can be a useful adjunct.
影响因子（Impact Factor）是医学期刊的主要绩效指标，它一直饱受批评，因为它未能捕捉到文章的真正影响；偏向方法学论文；受到统计异常值的不当影响；以及考察的时间段太短，无法捕捉文章的长期重要性。此外，在搜索引擎时代，读者不必浏览期刊就能找到信息，因此影响因子对引文效率的重视可能不合适。一个更好的指标将考虑期刊发表的所有论文的总引文数（不仅是最近的论文），并且不会因发表的论文总数而减少。我们提出了一个体现这些原则的指标，“内容因子（Content Factor）”，并检查了它在领先的医学和矫形外科期刊中的表现。为了纠正影响因子对近期引文的重视，内容因子考虑了所有引文的总数，而不管引用论文的发表年份。为了纠正影响因子对效率的重视，不使用分母。因此，内容因子是给定年份中期刊以前发表的所有论文的总引文数。我们发现内容因子和影响因子相关性较差。我们进一步调查了 75 名经验丰富的矫形外科作者，并衡量了他们对各种矫形外科杂志的“重要性”的看法。重要性评分与影响因子之间的相关性仅为 0.08；重要性评分与内容因子之间的相关性为 0.56。因此，内容因子更好地反映了期刊的“重要性”。总之，虽然内容因子不能作为唯一的绩效指标，但在绩效数据影响期刊评估的程度上，内容因子——一个易于获得且直观吸引人的期刊知识贡献指标，不受游戏影响——可以作为一个有用的补充。
