Guest Post: Measuring Impact in the field of Microbiology
How do we judge whether a research paper is any good? One straightforward way is to measure how often the article is downloaded online – but that doesn’t tell us if the readers actually thought the article was significant once they’d read it. Instead we can monitor how often an article is cited in the writings of other scientists. We can even do this for all the articles published by a particular journal (for example, in the last two or five years) and divide the total cites by the number of articles published to get an impact factor: Bingo, journal impact instantly measured!
Impact factors are a flawed and derided metric but – whisper it – by and large they also reflect many microbiologists’ perceptions and prejudices about the status of the journals in which we publish. When drafting a manuscript, it’s likely that each of us approaches choosing which journal we want to submit our work to in much the same way: we assess the scope and significance of the piece of work to be written up and then have a gut instinct as to which journal will accept it.
Typically we’ll aim as high as we can and reassure ourselves that if it’s ‘bounced’ (rejected) by X we can always submit to Y. Broadly this hierarchy of journals maps pretty well onto the impact factor rankings and, within that, it’s possible to see some clear divisions that be compared to football leagues.
Aside from the ‘Champions League’ of general science journals (Nature, Science, PNAS), there’s a well-established Premier League, which even has its own ‘Big Four’ (PLoS Pathogens, Molecular Microbiology, Cellular Microbiology, Environmental Microbiology) and its steady performers (notably the suite of ASM Journals such as Journal of Bacteriology). The tier below contains some well-regarded players (the SGM’s Microbiology, FEMS Microbiology Ecology), and the lower leagues perform valuable functions by providing a home for sound but less stellar science (and in many cases provides an outlet for the work of developing scientists, much as the lower leagues can develop football talent).
Occasionally, specific articles from the lower league journals can have a big individual impact, the equivalent (in this increasingly strained metaphor) of a Cup ‘giant killing’. Antonie van Leeuwenhoek, the journal I edit, bobbles around as a steady performer in the lower leagues, and I like to think we score some good away goals (a recent paper on bacterial evolution by Radhey Gupta may be one such article: only time will tell).
One difference between the league table for journals and the football leagues is with regard to promotion and relegation, as typically there’s not too much movement between divisions. However, recently new Open Access (OA) journals (notably the PLoS portfolio) have moved the goalposts and broken into the rankings, and others (such as ASMs recently launched mBIO) will undoubtedly follow. will undoubtedly follow. The Wellcome Trust is part of a consortium that has recently announced its intention to launch an OA Champions League contender.
Even though the annual impact factor updates don’t tend to throw up many surprises, it’s interesting to see a few in the recently released 2010 figures. Most surprising is that the impact factor for Molecular Microbiology seems to be in decline, despite the fact recent years have seen an apparent increase in the scale and scope required of studies by the journal’s editors. In contrast, this year has seen a notably improved impact factor for Environmental Microbiology and a respectable first impact factor for its new sister journal Environmental Microbiology Reports. Within the lower leagues, there are some steady improvers (Systematic and Applied Microbiology; Anaerobe) whereas the International Journal of Systematics and Evolutionary Microbiology continues its decline, most likely due to the increasingly large numbers of descriptions of new microbial species it publishes each year. Disappointingly, the Antonie van Leeuwenhoek impact factor dropped this year but only within our normal ‘wobble’ – with luck next year we’ll have bounced back, perhaps driven by the work of the microbelog contributors!
Iain Sutcliffe is Chair of Microbiology at Northumbria University (Newcastle upon Tyne) and Editor-in-Chief of Antonie van Leeuwenhoek Journal of Microbiology. His research focuses on the cell envelopes of bacteria, in particular membrane-anchored molecules.
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