The Citation Culture

The widespread use of rankings of journals in research institutes and universities creates a disadvantage for interdisciplinary research in assessment exercises such as the British Research Excellence Framework. This is the conclusion of a paper presented at the 2011 Annual Conference of the Society for the Social Studies of Science in Cleveland (US) by Ismael Rafols (SPRU, Sussex University), Loet Leydesdorff (University of Amsterdam) and Alice O’Hare, Paul Nightingale and Andy Stirling (all SPRU, Sussex University). The study is the first quantitative proof that researchers working at the boundaries between different research fields may be disadvantaged compared with monodisciplinary colleagues. The study argues that citation analysis, if properly applied, is a better measurement instrument than a ranked journal list.

The study is quite relevant for research management at universities and research institutes. Journal lists have become a very popular management tool. In a lot of departments, researchers are obliged to publish in a limited set of journals. Some departments, for example in economics, have even been reorganized on the basis of having published in such a list. The way these lists have been composed does vary. Sometimes a group of experts decides whether a journal belongs to the list, sometimes the Journal Impact Factor published by ISI/Thomson Reuters is the determining factor.

The study by Rafols et al. has analyzed one such list: the ranked journal list used by the British Association of Business Schools. This list is based on a mix of citation statistics and peer review. It ranks scholarly journals in business and management studies in five categories. “Modest standard journals” are category 1, “world elite journals” are category 4*. This scheme reflects the experience researchers have with the Research Assessment Exercise categories. The ranked journal list is meant to be used widely for a variety of management goals. It is used as an advice for researchers about the best venue for their manuscripts. Libraries are supposed to use it in their acquisition policies. And last but not least, it is used in research assessments and personnel evaluations. Although the actual use of the list is an interesting research topic in itself, we can safely assume that it has had a serious impact on the researchers in the British business schools community.

The study shows first of all that the position of a journal in the ranked list correlates negatively with the extent of interdisciplinarity of the journal. In other words, the higher the ranking, the more narrow its disciplinary focus. (The study has used a number of indicators for interdisciplinarity by which different aspects of what it means to be interdisciplinary have been captured.) Rewarding researchers to publish first of all in the ranked journal list may therefore discourage interdisciplinary work.

The study confirms this effect by comparing business and management studies to innovation studies. Both fields are subjected to the same evaluation regime in the Research Excellence Framework. Intellectually, they are very close. However, they differ markedly with respect to their interdisciplinary nature. Researchers in business schools have a more traditional publishing behaviour than their innovation studies colleagues. The research units in innnovation studies are consistently more interdisciplinary than the business and management schools.

Of course, publication behaviour is shaped by a variety of influences. Peer review may be biased against interdisciplinary work because it is more difficult to assess its quality. Many top journals are not eager to publish interdisciplinary work. This study is the first to show convincingly that these already existing biases tend to be made even stronger by the use of ranked journal lists as a tool in research management. The study confirms this effect by comparing the performance based on the ranked journal list with a citation analysis. In the latter, the innovation studies research is not punished by its more interdisciplinary character which does happen in an assessment on the basis of the journal list. The paper concludes with a discussion of the negative implications in terms of funding and acquiring resources for research groups working at the boundaries of different fields.

The paper will be published in a forthcoming issue of Research Policy and has been awarded the best paper at the Atlanta Conference on Science and Innovation Policy in September 2011.

Reference: Ismael Rafols, Loet Leydesdorff, Alice O'Hare, Paul Nightingale, & Andy Stirling, “How journal rankings can suppress interdisciplinary research. A comparison between innovation studies and business & management,” Paper presented at the Annual Meeting of the Society for the Social Studies of Science (4S), Cleveland, OH, Nov. 2011; available at http://arxiv.org/abs/1105.1227.

Recently, the new Times Higher Education World University Rankings 2011-2012 saw the light. The ranking revealed that Harvard University is no longer number one on the list. Incidentally, the differences with Caltech - now highest - are minimal. The main reason for Caltech’s rise are the extra revenues it drew out of industry. Caltech’s income increased by 16%, thereby outclassing most other universities. Harvard scored a bit better when it comes to the educational environment. Other universities also rose on the list as a result of a successful campaign to obtain (more) external financing. The London School of Economics, for example, moved from 86 to 47. The top of the ranking did not change that drastically though. Rich US-based universities still dominate the list. 7 out of ten universities highest on the list, and one third of the top 200, are located in the US.

This illustrates the THE ranking’s sensitivity to slight differences between indicators that, taken together, shape the order of the ranking. The ranking is based on a mix of many different indicators. There is no standardized way to combine these indicators, and therefore there inevitably is a certain arbitrariness to the process. In addition, the THE ranking is partly based on results of a global survey. This survey invites researchers and professors to assess the reputation of universities. One of the unwanted effects of this method is that well-known universities are more likely to be positively assessed than less popular universities. Highly visible forms of maltreatment and scandals may also influence survey results.

This year, the ranking’s sensitivity to the ways in which different indicators are combined is aptly illustrated by the position of the Dutch universities. The Netherlands are at number 3, with 12 universities in the top 200 and 4 in the first 100 of the world. Given the size of the country, this is a remarkable achievement. The result is partly caused by a strong international orientation of the Dutch universities, and partly by previous investments in research and education. But just as important is the weight given to the performances of the social sciences and humanities in a number of indicators. Compared to last year, the total performance of Dutch universities most likely did not increase that much. A more likely explanation is that the profile of activities and impact are better covered by the THE ranking.

The latest THE ranking does make clear that size is not the most important determinant in positioning universities. Small specialized universities can end up quite high on the list.

On November 16, 2011, the Rathenau Institute and the VU University Amsterdam organize a symposium on Dynamics of Academic Leadership. The symposium addresses the conditions that are necessary for high level performance and creativity in research, and the implications for research management and policy. Paul is one of the invited speakers. He will discuss some of the programmatic aspects and preliminary results of a large European FP-7 project: Academic Careers Understood through Measurement and Norms (ACUMEN). ACUMEN is aimed at understanding the ways in which researchers are evaluated by their peers and institutions, and at assessing how the science system can be improved and enhanced. The project is a cooperation among several European research institutes, with Paul as the principal investigator and CWTS's Clifford Tatum as project manager.

A recent landmark in the field of science mapping is Katy Börner’s Atlas of Science: Visualizing What We Know (MIT Press, 2010). The atlas recently won the ASIS&T Best Information Science Book Award 2011. The kinds of maps covered by the atlas range from historical timelines, network diagrams and citation networks revealing rises in patent citations, to geographic maps, taxonomic hierarchies and maps of relative sizes and connectedness of scientific fields.

The advent of science mapping depends to a large extent on digitized indices of scholarly activity such as the Science Citation Index, and on advances in network analysis and visualization techniques. Bibliometric maps of scholarly activity are mostly based on bibliographic coupling, co-citation analyses or maps of keywords based on a co-occurrence network. The visualizations that are created are transformations of quantified data into visual form. The avalanche of bibliometric data incorporated in massive databases demand new visualization tools and  - crucially – the skills to understand and engage with these new kinds of visualizations.

Most bibliometric mapping endeavors radiate an ambition on the part of the scientist(s) producing these maps to be synthetic, comprehensive and definitive. Börner’s Atlas of Science, for instance, is said to chart “the trajectory from scientific concept to published results,” revealing “the landscape of what we know.” However, maps are not a direct reflection of reality, all sorts of decisions are taken to process the data before they can be presented. While this may seem a matter 'of course', it does have consequences for the interpretation and  use of these maps.

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“My research: > 185 papers, h-index 40.” A random quote from a curriculum vitae in the World Wide Web. Sometimes, researchers love their Hirsch index, better known as the h-index. But what does the measure actually mean? Is it a reliable indicator of scientific impact?

Our colleagues Ludo Waltman and Nees Jan van Eck have studied the mathematical and statistical properties of the h-index. Their conclusion: the h-index can produce inconsistent results. For this reason, it is actually not the reliable measure of scientific impact that most users think it is. As a leading scientometric institute, we have therefore published the advice to all universities, funders, and academies of science to abandon the use of the h-index as a measure of the overall scientific impact of researchers or research groups. There are better alternatives. The paper by Waltman and Van Eck is now available as a preprint and will soon be published by the Journal of the American Society for Information Science and Technology JASIST.

The h-index is a measure of a combination of productivity and citation impact. It is calculated by ordering the number of publications by a particular researcher on the basis of the total number of citations they have received. For example, someone who has an h-index of 40 has published at least 40 articles that have each been cited at least 40 times. Moreover, the remaining articles have not been cited more than 40 times each. The higher the h-index the better.

The h-index was proposed by physicist Jorge Hirsch in 2005. It was an immediate hit. Nowadays, there are about 40 variants of the h-index. About one quarter of all articles published in the main scientometric journals have cited Hirsch’ article in which he describes the h-index. Even more important has been the response by scientific researchers using the h-index. The h-index has many fans, especially in the fields that exchange many citations, such as the biomedical sciences. The h-index is almost irrresistable because it seems to enable a simple comparison of the scientific impact of different researchers. Many institutions have been seduced by the siren call of the h-index. For example, the Royal Netherlands Academy of Arts and Sciences (KNAW) in the Netherlands inquires about the value of the h-index in its recent forms for new members. Individual researchers can look up their h-index based on Google Scholar documents via Harzing’s website publish or perish. Both economists and computer scientists have produced a ranking of their field based on the h-index.

Our colleagues Waltman and Van Eck have now shown that the h-index has some fatal shortcomings. For example, if two researchers with a different h-index co-author a paper together, it may lead to a reversal of their position in an h-index based ranking. The same may happen when we compare research groups. Suppose we have two groups and each member of group A has a higher h-index than a paired researcher in group B. We would now expect that the h-index of group A as group is also higher than that of group B. Well, that does not have to be the case. Please note that we are now speaking of a calculation of the h-index based on a complete and reliable record of documents and citations. The problematic nature of the data if one uses Google Scholar as data source is a different matter. So, even when we have complete and accurate data, the h-index may produce inconsistent results. Surely, this is not what one wants using the index for evaluation purposes!

At CWTS, we have therefore drawn the conclusion that the h-index should not be used as measure of scientific impact in the context of research evaluation.