Most participants in the scholarly publishing process take a keen interest in the journal impact factor, a yearly metric issued by Thomson Reuters. The 2010 IFs were just released and the news for ACerS journals is very good.
Of the three journals the American Ceramic Society publishes through its partner, Wiley—Journal of the American Ceramic Society, International Journal of Applied Ceramic Technology and International Journal of Applied Glass Science—JACerS and ACT are ranked in the top ten in the category Materials Science – Ceramics. The JACerS IF increased an impressive 11.5 percent over its 2009 value.
The JACerS IF is 2.167, the second highest for journals in the ceramic materials category. The ACT IF suffered some, dropping to 1.28 from its 2009 level of 1.627, but was still high enough to rank it in the top ten ceramics journals. IJAGS is too young to have an IF calculation. The Journal of the European Ceramic Society had the highest 2010 IF, experiencing an increase to 2.574 from its 2009 IF of 2.09.
What is the “impact factor?”
The IF is just one of the metrics used in the Journal Citation Reports that Thomson Reuters publishes yearly, and is probably its most visible metric. IF metrics were developed by the now-defunct Institute for Scientific Information, which has been absorbed into the Thomson Reuters organization.
In a general sense, the IF is a measure of the influence and relevance of a journal. The ISI formula¬¬-sometimes called the 2-year IF-is:
IF = Number of current year citations to the journal articles published in the two years prior/Number of articles published in the journal in the two years prior.
Therefore, the 2010 IF numerator is the number of citations (in any journal) during 2010 to articles published by the journal in 2008 and 2009. The denominator is the total number of articles published by the journal in 2008 and 2009. In 2010, JACerS articles from 2008-09 were cited 2815 times, and the number of articles published in 2008-09 was 1299, giving the IF of 2.167.
IF is a useful metric, but it is important not to overemphasize it.
JACerS senior journal editor, David Green said in an email communication, “Impact factor can be influenced by several extrinsic factors. For example, the rate of publication can influence IF. As an exaggeration, it would inflate the IF if all papers were published in January rather than spread through the year.” He also noted that papers published online before print can influence IF.
Also, because it is a ratio, it is informative to look at metrics other than just the IF. (An oceanographer might ask, which is more impactful: a tall, skinny wave or a squat, wide wave?)
The simplest of metrics is the number of citations per year. This number does not contribute to the IF because it covers all years and does not separate out the two-year-prior base of citations used in the IF calculation. But, it does give some “order of magnitude” perspective that can inform IF interpretations. For ceramic journals, JACerS is ranked first by a large margin, with over 29,000 citations in 2010. The closest competitor is the Journal of Non-Crystalline Solids (19, 500 cites; IF 1.483) followed by the J. Eur. Ceram. Soc. (12,600 cites).
Another metric is the “Immediacy Index,” which is the average number of times an article is cited in the year it is published. This year the J. Eur. Ceram. Soc. had the highest II of ceramics journals and JACerS the second highest. Similar to IF, it can be affected by extrinsic factors like the timing of publications, early online publication, etc.
While IF and II are indicators respectively of recent and very short term interest in a journal’s articles, the long term value of a journal’s articles is even more important.
There are two metrics that indicate the effectiveness of journal editors at selecting high quality articles: the “5-year IF” and the “Cited Half-life.” The 5-IF is the same as the 2-year IF but captures the relevance of a journal’s articles over the longer time span. It helps normalize the effects of things that can skew the importance of the literature, like trendy science and “funding flashes.” On this metric, JACerS ranks first with a 5-IF of 2.37, followed by J. Eur. Ceram. Soc. at 2.265.
Finally, the “Cited Half-life” measures the median age of articles cited in the current JCR year, that is, the long-term relevance of articles and the level of fundamental scholarship that the journal offers. In the field of ceramics, JACerS and Phys. Chem. Glasses-B lead with a CHL of over 10 years. Green says, “A large Cited Half-life shows the fundamental nature of JACerS articles, as they will be referred to for many years.”
ACT‘s cited half-life is 4.3 years, impressive because 2010 was only its seventh year of publication.
Factors other than metrics should be considered by scientists when they are deciding where to submit papers, and Green recommends taking a broad view, “For example, they should consider whether the review process is fair, thorough and adds value to their papers.” He suggests authors ask themselves, “Was the submission process friendly? Are the published figures of high quality with the appropriate resolution? Is the text clear and understandable? Are the articles in the journal based on fundamental science that incorporates the Scientific Method? Are the articles published rapidly and do they describe new discoveries? Does the journal have a global reach?”
The Thomson Reuters website has in-depth information about IF and other metrics that go into the Journal Citation Reports.