A measure of the esteem in which a peer-reviewed paper is held is supposedly the number of times to which it is referred in other papers. Of course, the older a paper is the more chance that such citations will have built up; but the annual rate of citation is likely to fizzle out over time. Papers that create a frisson of initial excitement and command enduring citation are few and far between: they probably launched a new line of inquiry.
It is instructive to try to nail Alfred Wegener’s influence in tectonics using the Web of Science, which ought to have been pretty high. Superficially, he had none and is remembered through that arm of Thomson Reuters for six papers: four on atmospheric physics – his speciality; one on lunar craters and a sixth on the patterns of cracking seen on rotten wood. These give him a mere 20 citations. Wegener’s posthumous problem was that Die Entstehung der Kontinente first appeared in the fourth issue of Geologische Rundshau in 1912, and seemingly the Web of Science doesn’t have that journal in its archives of a century ago. Later, extended editions appeared in book format which were not peer reviewed (most geoscientists would not touch his ideas with a barge pole until long after his death in 1930), and are therefore outside the academic pale. The key to a plausible mechanism for continental drift – symmetrical magnetic striping above ocean basins – was first described by Fred Vine and Drummond Matthews in an issue of Nature in 1963. In 50 years their work, ranking with discovering the structure of DNA, has accumulated 709 citations; i.e. 38.5 citations per year on average, which is not much for fuelling a revolution.
Of course, citation is not the same as the frequency at which a paper is read. It is no secret that a not inconsiderable number of papers that appear in published reference lists haven’t been read by the authors who cite them. They are there by proxy, and you will probably find them in the bibliography of later papers that those same authors have cited. There is perhaps a certain kudos in such proxy citations, for it may be that the cited paper has achieved the equivalent of canonical status in the field.
Citation frequency is something of a lottery: language of publication; discipline (since 1953 Crick and Watson achieved three times Vine and Matthews’s average citations); date of publication (E. Komatsu of the University of Texas at Austin has already had 1939 citations for his February 2011 paper ‘Seven-Year Wilkinson Microwave Anisotropy Probe Observations: Cosmological Interpretations’ published in a supplement to the Astrophysical Journal; nine times the rate of Crick and Watson, but the paper is about the origin of everything)
Interestingly, the December 2012 issue of Geology presents stats on the most cited papers that it has published since 2000 (Cowie, P.A. 2012. Highly cited Geology papers (2000-2010) – What were they and who wrote them? Geology, v. 40, p. 1147-1148). Geology is among the highest ranking journals in the geoscience field, and had an impact factor of 4.8 over the last 5 years. A journal’s impact factor is the number of times all articles published in a 2-year period were cited in all indexed journals in the year following them, divided by the total number of articles published in the two years by the assessed journal. So, papers published in Geology between2007 and 2011 were cited on average 4.8 times in the year following publication. This journal is a useful source of citation statistics as it covers the full range of geoscience and all papers are limited to 4 printed pages, thereby forcing authors to be concise and clear in their writing and illustration. Consequently it is popular, which, incidentally, may explain its high impact factor.
Of the 33 papers cited most between 2000 and 2010, 14 are on topics relating to Tibet and China. There are 3 on oceanography; 3 on paleontology and extinctions; 6 on palaeoclimatology; 10 on tectonics and 10 on magmatism (3 of which were about rare adakites formed by partial melting of subducted oceanic crust). I haven’t read all of the papers, and the stats on topics may tell us very little, but I would bet that papers about geology in high-population emerging countries – China, India and Brazil – are met gleefully by rapidly growing communities of eager young geoscientists. It may even be worth a flutter on adakites as the ‘next big thing’ in petrogenesis. Mind you, it looks like I am not likely to be the best punter for hot papers, as out of the 33 ‘top-3′ papers since 2000, only 6 made it into Earth Pages, and of those only one between 2004-2010.
The digest goes on to show that year-by-year as many as 10 % of papers in Geology are not cited at all, up to 70% are cited between 1 and 5 times per year, while less than 10% get 10 or more citations in a year. Oddly, the author suggests that a dip in citations of Geology papers in recent years may reflect the launch of Nature Geoscience in 2008. Yet glossy as that new addition to the Nature stable might be, it has become something of a desert for papers on geology. Then there is evidence for both ‘vintage’ and ‘just-about-drinkable’ years in Geology citations: the ‘top ten’ papers in 2001, 2005, 2006, 2008 and 2010 ranged from 10-15 citations for the tenth to 20-25 for the ‘hottest’ paper, while in 2000, 2002, 2003, 2004, 2007 and 2009 the most cited papers stood well above the rest at 32 to 55 citations per year. But that may just reflect the uneven pace at which well-received and provocative work emerges.
So, it begins to seem, from Geology at least, that for most geoscience authors publishing isn’t going to raise much hope as far as jobs or promotions are concerned. Yet if results are not published funding agencies may become fractious about your next grant application, and of course, university science departments puff themselves with annual publication rates (though rarely citation records, which as far as geosciences goes could be a wise move). But it is a matter of academic duty to publish for the record; even if a paper fills just one tiny niche the cumulative effect of publically available knowledge does eventually result in breaks through – one never knows… It could be a salutary lesson should publishers release data on hits for on-line PDFs of papers, as that would give some indication of how many readers individual papers have, but as for a ‘like this’ button or a means of star rating I think we have to venture into the deeper recesses of academic conservatism one small step at a time.
- Is the Relationship Between Journal Impact Factors and Article Citations Growing Weaker? (scholarlykitchen.sspnet.org)
- How Much of the Literature Goes Uncited? (scholarlykitchen.sspnet.org)
- Study reveals declining influence of high impact factor journals (eurekalert.org)