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The data in the present analysis was tentatively divided into two groups in order to discriminate between the fundamental studies of bibliometric analysis concerning theoretical issues and the more applied studies. This was done for both the studies and the citing articles. It is also evident by assigning different codes or descriptors to the ILS-articles that a large fraction can be classified as “subject” based studies and must be placed in its own subcategory. This is another division of the literature than used by Jonkers and Derrick (2012) who dealt with multidisciplinary science as a separate classification and analyzed it as a non-ILS subcategory. In this way multidisciplinary studies are represented in ILS as well as non-ILS literature and the analysis in the two groups complement each other. The data concerning the absolute number of articles in the ILS and the non-ILS category is comparable to the almost exponential growth recorded during the last two decades by Jonkers and Derrick (2012). They found a substantial increase in the number of publications about development and improvement of bibliometric indicators as well as methods during recent years in both the ILS category and, although to a lesser extent, the non-ILS category. In the present data, the fundamental studies (tier 2) are published in a small number of “Information and Library Science” journals with Scientometrics and Journal of the American Society for Information Science and Technology (JASIST) as the leading publishing channel. A large number of “applied” studies are still published in the “Information and Library Science” journals (tier 3), which accounts for about 2/3 of the articles. The journal Scientometrics, established in 1978, published 60 % of all the applied studies in this group while the number in case of the theoretical studies (tier 2) is only 45 %. The same numbers in case of JASIST are 17 and 8 % percent respectively which makes Scientometrics the leading journal for applied bibliometric studies.
The applied non-ILS based studies in tier 4 are found in a much larger number of different “subject” oriented journals, which reflects the multidisciplinary relevance of these articles for the professional communities.
Our time-lapse data further shows that there are relatively few articles on bibliometric analysis before 1994. It is almost as if there was a threshold for this type of publications and it is probably due to a number of factors: Firstly, the need for a sufficient volume of materials to become analyzed and second, the advancement of computerized methods for data treatment and the general availability of electronic versions of well-established databases such as SCI. The emergence and widespread distribution of the internet and the World Wide Web within the scientific communities also made data gathering easier. Of course, the general awareness and hence demand for these types of analysis plays a significant role.
The studies published in the non-ILS category grew more dominant through this period probably due to more focus on research performance evaluation, while the number of theoretical studies was relatively constant. This is in spite of the fact that a large number of articles on different modifications of bibliometric indicators have emerged in the wake of the paper about the h-index published by Hirsch (2005). These studies are most likely to be found among the tier 2 articles.
The citation rate is not very different for the articles in the four different tiers investigated here, although theoretical studies, indexed in the ILS category, tend to be the most cited. This result is in accordance with the study of Jonkers and Derrick (2012) who use field-normalized citation data. One could indeed predict and expect reasonably lower citation rates for the “subject” based types of analysis. These studies are more suited for a smaller professional community within the field, not a general audience. The possibility exists that the practitioners in the fields which are targeted by non-ILS publications are less likely to make literature contributions that appreciate bibliometric studies of the field via citations (Derrick et al. 2012). One could simply state that to this community, it is the results of the bibliometric analysis which is the most important and not the analytical process itself. Of course, it certainly places a greater responsibility on the ILS-community to make sure that the tools and methods of bibliometrics are adequately described and available for use.
The above pattern is reflected again in the number of citing articles and journals. The number of citing articles per journal is very large for ILS articles cited in the same category. The articles classified in the non-ILS category are still cited in many journals but by far the largest number of citing journals is also found in the non-ILS category. This shows that articles that refer to bibliometric analysis are not only scattered around in many “subject” based journals but are cited with the same frequency in the similar type of journals as well. The applied studies in tier 3 are cited more equally in the ILS and non-ILS articles. From 1994 onwards, library citations dominated but from around 2008, the non-ILS citations caught up. This illustrates the importance of choosing your publication channel. There are relatively more citations within the same category. The peers of the authors of a publication expect to read, publish and cite in similar journals.
On the other hand this statement could be seen in a different light when we consider the theoretical or methodical non-ILS articles in tier 2. They are cited in almost the same manner as the applied articles. Apparently, the methodical studies are well noticed by the non-ILS community as well.
If we look at the absolute number of articles that cite articles in the non-ILS category, citations within the same category are dominating. This trend becomes clear from 1994- onwards. The number of citations from “subject” articles is also larger up to 1994, however, most citations are found in the journal Current Contents. During this period, many columns in this weekly journal treated the fundamental, intrinsic problems with the use of the bibliometric analysis as a working tool. Up to the year 1992, 439 out of 898, representing almost half of all citations, are registered in Current Contents. The journal could reasonably be placed in the ILS-category but the division used by WoS in the earlier work of Jonkers and Derrick (2012) was maintained.
The normalized data indicates a major difference between the ILS and non-ILS field. While the impact of the non-ILS publications continues to rise at a steady pace within the community itself, the impact is more constant in the ILS community. Obviously, the application of bibliometric methods becomes more and more accepted by the community who were the original target of these methods, and it is honored via citations. Similar publications in ILS journals receive rising awareness from both the ILS and the non-ILS community. This last finding is important because the development of the bibliometric field will benefit from a closer interrelationship between the groups, especially in times when new metrics and indicators enter the field. Indeed, the data, especially in tier 3, indicates interrelations between the ILS and non-ILS communities and increased participation of bibliometricians in tier 4 publications could further professionalize the field. The whole science of bibliometry could indeed benefit from border crossing between the applied and non-applied fields. Bibliometricians could demonstrate the methods available in a practical context and in the same manner, the co-operation with the professional, “subject” orientated communities could improve the theoretical development of the field. The normalized citation data for both tier 3 and tier 4 reached an all-time low around 1997 and 1994, respectively. Obviously, apart from the scarce data, both tiers became less cited up to the period when bibliometric tools and data became available on-line. The following increase is clearly correlated to the similar increase in the number of articles about bibliometric analysis observed around the same time period for both tiers as shown in Fig. 2. Actually, the increase in number of publication in tier 3 lags behind the data of tier 4. This could explain the similar 3-year lag in the normalized citation data.
Next, we turn to the subjects studied. The use, publication and citation pattern are similar for the applied, health, physical and life sciences. Computer science has a lower impact within the community. This could, in itself, be due to the fact that this field is regarded as fast moving and therefore its literature is seen as having a shorter lifespan.
By far the highest citation rate is gained by publishing bibliometric analyses of multidisciplinary studies. This can, of course, be explained by the fact that the sheer number of people involved is higher and probably, according to InCites.Essential Science Indicators (2015) in a higher impact of multidisciplinary studies itself, but the assumed beneficial effects of cooperation between scientific groups apparently also show up in the bibliometric analysis of this literature type. We believe this issue deserves more attention.
Our findings show clearly how a number of countries have dominated the field of bibliometric analysis and still partially do. USA, PRC and England are the leading countries but the number of articles published by authors from Spain and The Netherlands is also noteworthy. The articles from the latter country are not very numerous but their impact is far greater. As an example, the Centre for Science and Technology Studies in Leiden, established in 1989, is a well-reputed institution for fundamental bibliometric research. It is well known that country indicators are sensitive to the delimitation of journals included in the investigation, and the leading countries are particularly present in high-impact journals (Zitt et al. 2003).