Bibliometrics of individual researchers

The demand for measures of individual performance in the management of universities and research institutes has been growing, in particular since the early 2000s. The publication of the Hirsch Index in 2005 (Hirsch, 2005) and its popularisation by the journal Nature (Ball, 2005) has given this a strong stimulus. According to Hirsch, his index seemed the perfect indicator to assess the scientific performance of an individual author because “it is transparent, unbiased and very hard to rig”. The h-index balances productivity with citation impact. An author with a h-index of 14 has created 14 publications that each have been cited at least 14 times. So neither authors with a long list of mediocre publications, nor an author with 1 wonder hit are rewarded by this indicator. Nevertheless, the h-index turned out to have too many disadvantages to be wearing the crown of “the perfect indicator”. As Hirsch acknowledged himself, it cannot be used for cross-disciplinary comparison. A field in which many citations are exchanged among authors will produce a much higher average Hirsch index than a field with much less citations and references per publication. Moreover, the older one gets, the higher ones h-index will be. And, as my colleagues have shown, the index is mathematically inconsistent, which means that rankings based on the h-index may be influenced in rather counter-intuitive ways (Waltman & Eck, 2012). At CWTS, we therefore prefer the use of an indicator like the number (or percentage) of highly cited papers instead of the h-index (Bornmann, 2013).

Still, none of the bibliometric indicators can claim to be the perfect indicator to assess the performance of the individual researcher. This raises the question of how bibliometricians and science managers should use statistical information and bibliometric indicators. Should they be avoided and should the judgment of candidates for a prize or a membership of a prestigious academic association only be informed by peer review? Or can numbers play a useful role? What guidance should the bibliometric community then give to users of their information?

This was the key topic at a special plenary at the 14th ISSI Conference two weeks ago in Vienna. The plenary was an initiative taken by Jochen Gläser (Technical University Berlin), Ismael Rafols (SPRU, University of Sussex, and Ingenio, Polytechnical University Valencia), Wolfgang Glänzel (Leuven University) and myself. The plenary aimed to give a new stimulus to the debate how to apply, and how not to apply, performance indicators of individual scientists and scholars. Although not a new debate – the pioneers of bibliometrics already paid attention to this problem – it has become more urgent because of the almost insatiable demand for objective data and indicators in the management of universities and research institutes. For example, many biomedical researchers mention the value of their h-index on their CV. In publications lists, one can regularly see the value of the Journal Impact Factor mentioned after the journal’s name. In some countries, for example Turkey and China, one’s salary can be determined by the value of either the h-index or the journal’s impact factor one has published in. The Royal Netherlands Academy of Arts and Sciences also seems to ask for this kind of statistics in its forms for new members in the medical and natural sciences. Although robust systematical evidence is still lacking (we are working hard on this), the use of performance indicators in the judgment of individual researchers for appointments, funding, and memberships, seems widespread, intransparent and unregulated.

This situation is clearly not desirable. If researchers are being evaluated, they should be aware of the criteria used and these criteria should be justified for the purpose at hand. This requires that users of performance indicators should have clear guidelines. It seems rather obvious that the bibliometric community has an important responsibility to inform and provide such guidelines. However, at the moment, there is no consensus yet about such guidelines. Individual bibliometric centres do indeed inform their clients about the use and limitations of their indicators. Moreover, all bibliometric centres have the habit of publishing their work in the scientific literature, often including technical details of their indicators. However, this published work is not easily accessible to non-expert users such as deans of faculties and research directors. The literature is too technical and distributed over too many journals and books. It needs synthesizing and translation into plain language which is easily understandable.

To initiate a process of a more professional guidance for the application of bibliometric indicators in the evaluation of individual researchers, we asked the organizers of the ISSI conference to devote a plenary to this problem, which they kindly agreed to. At the plenary, Wolfgang Glänzel and me presented “The dos and don’ts in individual level bibliometrics”. We do not think this is a final list, more a good start with ten dos and don’ts. Some examples: “do not reduce individual performance to a single number”, “do not rank scientists according to 1 indicator”, “always combine quantitative and qualitative methods”, “combine bibliometrics with career analysis”. To prevent misunderstandings: we do not want to initiate a bibliometric police with absolute rules. The context of the evaluation should always determine which indicators and methods to use. Therefore, some don’ts in our list may sometimes be perfectly useable, such as the application of bibliometric indicators to make a first selection among a large number of candidates.

Our presentation was commented on by Henk Moed (Elsevier) with a presentation on “Author Level Bibliometrics” and by Gunnar Sivertsen (NIFU, Oslo University) with comments on the basis of his extensive experiences in research evaluation. Henk Moed built on the concept of the multi-dimensional research matrix which was published by the European Expert Group on the Assessment of University Based Research in 2010, of which he was a member (Assessing Europe’s University-Based Research – Expert Group on Assessment of University-Based Research, 2010). This matrix aims to give global guidance to the use of indicators at various levels of the university organization. However, it does not focus on the problem of how to evaluate individual researchers. Still, the matrix is surely a valuable contribution to the development of more professional standards in the application of performance indicators. Gunnar Sivertsen made clear that the discussion should not be restricted to the bibliometric community itself. On the contrary, the main audience of guidelines should be the researchers themselves and adminstrators in universities and funding agencies.

The ensuing debate led to a large number of suggestions. They will be included in the full report of the meeting which will be published in the upcoming issue of the ISSI’s professional newsletter in September 2013. A key point was perhaps the issue of responsibility: it is clear that researchers themselves and the evaluating bodies should carry the main responsibility for the use of performance indicators. However, they should be able to rely on clear guidance from the technical experts. How must this balance be struck? Should bibliometricians refuse to deliver indicators when they think their application would be unjustified? Should the association of scientometricians publicly comment on misapplications? Or should this be left to the judgment of the universities themselves? The plenary did not solve these issues yet. However, a consensus is emerging that more guidance by bibliometricians is required and that researchers should have a clear address to which they can turn to with questions about the application of performance indicators either by themselves or by their evaluators.

What next? The four initiators of this debate in Vienna have also organized a thematic session on individual level bibliometrics at the next conference on science & tecnnology indicators, the STI Conference “Translational twists and turns: science as a socio-economic endeavour”, which will take place in Berlin, 4-6 September 2013. There, we will take the next step in specifying guidelines. In parallel, this conference will also host a plenary session on the topic of bibliometric standards in general, organized by iFQ, CWTS and Science-Metrix. In 2014, we will then organize a discussion with the key stakeholders such as faculty deans, adminstrators, and of course the research communities themselves on the best guidelines for evaluating individual researchers.

Stay tuned.


Assessing Europe’s University-Based Research – Expert Group on Assessment of University-Based Research. (2010). Research Policy. European Commission. doi:10.2777/80193

Ball, P. (2005). Index aims for fair ranking of scientists. Nature, 436(7053), 900. Retrieved from

Bornmann, L. (2013). A better alternative to the h index. Journal of Informetrics, 7(1), 100. doi:10.1016/j.joi.2012.09.004

Hirsch, J. E. (2005). An index to quantify an individual’s scientific research output. Proceedings of the National Academy of Sciences of the United States of America, 102(46), 16569–72. doi:10.1073/pnas.0507655102

Waltman, L., & Eck, N. J. Van. (2012). The Inconsistency of the h-index. Journal of the American Society for Information Science and Technology, 63(2007), 406–415. doi:10.1002/asi

6 Responses to “Bibliometrics of individual researchers”

  1. jbrittholbrook Says:

    Reblogged this on jbrittholbrook and commented:
    A vital debate for all researchers to stay tuned to!

  2. Ad Prins Says:

    For the almost inevitable use of bibliometrics for individuals, these are very helpful recommendations, but clearly it is vital that reviewers and review committees also join the discussion or at least get acquainted with the dilemma’s of bibliometrics in this kind of context. So, this is a good start, thank you!

  3. Article-Level Metrics – Learning to Walk, Run & Do Algebra | PLOS Tech Says:

    […] in the plenary. Their slides are available at Slideshare and Paul Wouters has also written a blog post about this session. The discussion continued today at the STI conference in […]

  4. Bibliometrics of individual researchers – the debate in Berlin | The Citation Culture Says:

    […] lively debate we had at the ISSI conference in Vienna continued at the STI2013 conference, “Translational […]

  5. Bibliometrisk etik? | bibliometri Says:

    […] diskussion följdes sedan upp vid STI konferensen i Berlin (Se Paul Wouters inlägg på samma tema här). Försöken att etablera standards och riktlinjer är tydlig också i den nyligen publicerade […]

  6. Aleksey Belikov Says:

    Great article! I have recently proposed a novel index for evaluation of individual researchers. Please have a look.

    A citation-based, author- and age-normalized, logarithmic index for evaluation of individual researchers independently of publication counts

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