Impact is a word we hear a lot about these days. In annual reviews, the question often asked is: “What is the impact of your research (or teaching or outreach) activities?” It is also becoming much more prevalent to provide documentation of your impact in a quantitative fashion, despite the difficulties in generating meaningful metrics. But such is the world we now live and work in. The situation is no different with journals.
Not surprisingly, the metric for the impact that journals have is provided by how widely cited they are, which presumably is related to how well read and used they are. The most popular metric is aptly named the “Impact Factor”. It is compiled in the Journal Citation Report, along with several other metrics, such as Immediacy Index, Eigenfactor, and Article Influence scores (Thomson Reuters, 2011). Although there has been much discussion about the use and misuse of impact factors (Barbarick et al., 2008; Garfield, 2006), it is one means we have of assessing the vitality of the Soil Science Society of America Journal (SSSAJ).
The impact factor of SSSAJ has trended upward for the past several years, and was 2.179 in 2009, the most recent year that the statistic is available; however, relative to the other 30 journals in the soil science category, this impact factor has been drifting downward, to seventh in 2009. Are there reasons for this downward trend and should there be cause for concern? To address these questions, I would like to provide some perspective based on longer term trends during the past few decades.
As with the rest of the scientific literature, the numbers of articles published in soil science journals has grown exponentially, increasing about 250% from the 1970s to the 2000s. This was accompanied by a doubling of the numbers of soil science journals. In that time span, the numbers of articles published in SSSAJ has increased modestly by about 10%. Thus, it is not surprising that the percentage of SSSAJ articles has declined by about one-third, from 23 to 8% of the total published in soils journals.
Numbers, however, do not tell the whole story. Assuming that the frequency of citations to articles published in a journal is indeed an index of impact, one metric is to examine trends in the percentage of highly cited articles published in SSSAJ. Based on the 1,000 most cited articles of each decade from all soils journals listed in the Journal Citation Report (Thomson Reuters, 2011), SSSAJ has remained one of the top three journals. In fact, relative to the percentage of articles published in SSSAJ, the percentage of highly cited articles has gradually increased with each decade.
Another trend during the past 40 years has been a large increase in the number of review articles published in soil science journals. Up until the last decade, <1% of all articles were reviews, but that has increased to 2% overall, and 1% in SSSAJ. Because reviews are generally more highly cited (12% of the 1000 most cited articles from 2000-2009)—at least during the short term—journals that publish more reviews than SSSAJ have moved up in the impact factor ratings.
To get back to my earlier questions, I think the short-term downward trend in the relative SSSAJ impact factor ranking is a manifestation of longer term trends in both a greater number of articles published in other soil science journals (our portion of the publishing pie is decreasing) and other journals more aggressively soliciting review manuscripts. It is less certain if these factors should be a cause for concern because our articles remain highly cited.
We will continue to seek after manuscripts that provide concise and insightful reviews on timely topics (please consider this an invitation!); however, our emphasis will remain on quality rather than quantity of reviews. Similarly, we welcome the submission of your best research efforts as original articles or notes, as we have room to grow SSSAJ into the future and thereby ensure that its impact continues.