The influence of author self-citations on bibliometric meso-indicators. The case of european universities

Summary In earlier studies by the authors, basic regularities of author self-citations have been analysed. These regularities are related to the ageing, to the relation between self-citations and foreign citations, to the interdependence of self-citations with other bibliometric indicators and to the influence of co-authorship on self-citation behaviour. Although both national and subject specific peculiarities influence the share of self-citations at the macro level, the authors came to the conclusion that - at this level of aggregation - there is practically no need for excluding self-citations. The aim of the present study is to answer the question in how far the influence of author self-citations on bibliometric meso-indicators deviates from that at the macro level, and to what extent national reference standards can be used in bibliometric meso analyses. In order to study the situation at the institutional level, a selection of twelve European universities representing different countries and different research profiles have been made. The results show a quite complex situation at the meso-level, therefore we suggest the usage of both indicators, including and excluding self-citations.     

Self-citations at the meso and individual levels: effects of different calculation methods

This paper focuses on the study of self-citations at the meso and micro (individual) levels, on the basis of an analysis of the production (1994–2004) of individual researchers working at the Spanish CSIC in the areas of Biology and Biomedicine and Material Sciences. Two different types of self-citations are described: author self-citations (citations received from the author him/herself) and co-author self-citations (citations received from the researchers’ co-authors but without his/her participation). Self-citations do not play a decisive role in the high citation scores of documents either at the individual or at the meso level, which are mainly due to external citations. At micro-level, the percentage of self-citations does not change by professional rank or age, but differences in the relative weight of author and co-author self-citations have been found. The percentage of co-author self-citations tends to decrease with age and professional rank while the percentage of author self-citations shows the opposite trend. Suppressing author self-citations from citation counts to prevent overblown self-citation practices may result in a higher reduction of citation numbers of old scientists and, particularly, of those in the highest categories. Author and co-author self-citations provide valuable information on the scientific communication process, but external citations are the most relevant for evaluative purposes. As a final recommendation, studies considering self-citations at the individual level should make clear whether author or total self-citations are used as these can affect researchers differently.     

The influence of author self-citations on bibliometric macro indicators

In a recent paper the authors have studied the role of author self-citations within the process of documented scientific communication. Two important regularities such as the relative fast ageing of self-citations with respect to foreign citations and the “square-root law” characterising the conditional expectation of self-citations for given number of foreign citation have been found studying the phenomenon of author self-citations at the macro level. The goal of the present paper is to study the effect of author self-citations on macro indicators. The analysis of citation based indicators for 15 fields in the sciences, social sciences and humanities substantiates that at this level of aggregation there is no need for any revision of national indicators and the underlying journal citation measures in the context of excluding self-citations. This revised version was published online in June 2006 with corrections to the Cover Date.     

A macro study of self-citation

This study investigates the role of self-citation in the scientific production of Norway (1981-1996). More than 45,000 publications have been analysed. Using a three-year citation window we find that 36% of all citations represent author self-citations. However, this percentage is decreasing when citations are traced for longer periods. We find the highest share of self-citation among the least cited papers. There is a strong positive correlation between the number of self-citations and the number of authors of the publications. Still, only a minor part of the overall increase in citation rates that can be found for multi-authored papers is due to self-citations. Also, the share of self-citation shows significant variations among different scientific disciplines. The results are relevant for the discussion concerning use of citation indicators in research assessments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Does co-authorship inflate the share of self-citations?

In recent papers, the authors have studied basic regularities of author self-citations. The regularities are related to the ageing, to the relation between self-citations and foreign citations and to the interdependence of self-citations with other bibliometric indicators. The effect of multi-authorship on citation impact has been shown in other bibliometric studies, for instance, by Persson et al. (2004). The question arises whether those regularities imply any relation between number of co-authors and the extent of author self-citations. The results of the present paper confirm the common notion of such effects only in part. The authors show that at the macro level multi-authorship does not result in any exaggerate extent of self-citations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Author self-citations in the field of ecology

Ecologists writing research articles frequently cite their own papers. Self-citations are frequent in science, but the reasons behind abnormally high rates of self-citations are questionable. My goals were to assess the prevalence of author self-citations and to identify the combination of attributes that best predict high levels of self-citations in ecology articles. I searched 643 articles from 9 different ecology journals of various impact factors for synchronous (i.e., within reference lists) and diachronous (i.e., following publication) self-citations, using the Web of Science online database. I assessed the effect of the number of authors, pages, and references/citations, the proportion of diachronous/synchronous self-citations, and the impact factor, on the proportion of synchronous and diachronous self-citations separately. I compared various candidate models made of these covariates using Akaike’s Information Criterion. On average, ecologists made 6.0 synchronous self-citations (12.8% of references), and 2.5 diachronous self-citations (25.5% of citations received 2.8 to 4.5 years after publication) per article. The best predictor of the proportion of synchronous self-citations was the number of authors. My study is the first to report recidivism in the inclusion of self-citations by researchers, i.e., the proportion of diachronous self-citations was best explained by the proportion of synchronous self-citations. The proportion of self-citations also increased with the number of pages and the impact factor of ecology journals, and decreased with the number of references/citations. Although a lot of variance remained unexplained, my study successfully showed regularities in the propensity of ecologists to include self-citations in their research articles.     

To cite or not to cite: author self-citations and the impact factor

Author self-citations are another factor that affects the impact factor of a journal. Typically these self-citations are just counted as such. But to be more meaningful I suggest that when examining the contribution of authors?? self-citations to impact factors one should first count the number of citations in the text rather than in the reference list, and then discriminate between different kinds of author self-citations??from those that are informative to those that are self-enhancing??if these data are to be more credible.     

Exploring the analytical potential of comparing citing and cited source items

Summary Comparing properties of citing and cited source items opens a wide variety of analytical possibilities. In a study of citations among papers in the journal Scientometrics a number of analytical themes are identified. The analysis shows: the way in which a citation graph can be decomposed into different subparts; country specific citation patterns; the effects of self-citations and domestic citations; the mapping of cited author relationships using direct citation and co-citation links; and time slicing effects on impact ranking of countries and papers.     

Some bibliometric correlates of quality in scientific research

The following kinds of data were collected on three samples of cancer research literature representing three levels of quality: (1) collaboration as measured by the number of authors per paper, (2) quantitative productivity of countries, (3) diachronous citations covering the first five years of publication, (4) total self-citations, (5) proportions of self-citations made by first-named authors, and (6) the extent of dispersion of articles among journals. Analyses showed that as the number of authors per paper increases, the proportion of high quality papers also increases and the Collaborative Index can be used to measure quality in the aggregate. It was found that the quantity and quality of cancer research done in a country are positively related. All analyses of the citation data confirmed the hypotheses that highly rated papers are significantly more highly cited than average papers and the rates of uncitedness decline with quality. The proportion of self-citations to total citations decreases with increasing quality and, on average, first-named authors of quality papers cite them proportionally fewer times than first-named authors of run-of-the mill papers do. This study also shows that, as quality increases, the extent of literature scatter or dispersion increases.     

Institutional self-citation rates: A three year study of universities in the United States

Using Institute for Scientific Information (ISI) data, this paper calculated institutional self citations rates (ISCRs) for 96 of the top research universities in the United States from 2005–2007. Exhibiting similar temporal patterns of author and journal self-citations, the ISCR was 29% in the first year post-publication, and decreased significantly in the second year post-publication (19%). Modeling the data via power laws revealed total publications and citations did not correlate with the ISCR, but did correlate highly with ISCs. California Institute of Technology exhibited the highest ISCR at 31%. Academic and cultural factors are discussed in relation to ISCRs.     

The efficiency of self-citations in economics

Summary Are prior self-citations an effective input in increasing a subsequent article's citation count? Examination of 418 articles in eight economics journals found that, after controlling for article length, journal and author quality, lead article position, and coauthorship, an author's prior stock of self-citations is not statistically related to a subsequent article's total citation count or the quality of the journals in which those citations appear. Self-citations that appear in prestigious high-impact economics journals have a statistically positive, but numerically small, effect on a subsequent article's total citation count and on the quality of the citing journal. The productive effect of a prior self-citation is inversely related to its age. Prior self-citations of the second author listed in a collaborative article have no significant effect on a subsequent article's total citation count or the quality of the economics journals in which those citations appear.     

Journals that increase their impact factor at least fourfold in a few years: The role of journal self-citations

The aim of this study was to ascertain the possible effect of journal self-citations on the increase in the impact factors of journals in which this scientometric indicator rose by a factor of at least four in only a few years. Forty-three journals were selected from the Thomson—Reuters (formerly ISI) Journal Citation Reports as meeting the above criterion. Eight journals in which the absolute number of citations was lower than 20 in at least two years were excluded, so the final sample consisted of 35 journals. We found no proof of widespread manipulation of the impact factor through the massive use of journal self-citations.     

A concise review on the role of author self-citations in information science, bibliometrics and science policy

Summary  The objective of the present study is twofold: (1) to show the aims and means of quantitative interpretation of bibliographic features in bibliometrics and their re-interpretation in research policy, and (2) to summarise the state-of-art in self-citation research. The authors describe three approaches to the role of author self-citations and possible conflicts arising from the different perspectives. From the bibliometric viewpoint we can conclude that that there is no reason for condemning self-citations in general or for removing them from macro or meso statistics; supplementary indicators based on self-citations are, nonetheless, useful to understand communication patterns.     

Preface

Summary  The objective of the present study is twofold: (1) to show the aims and means of quantitative interpretation of bibliographic features in bibliometrics and their re-interpretation in research policy, and (2) to summarise the state-of-art in self-citation research. The authors describe three approaches to the role of author self-citations and possible conflicts arising from the different perspectives. From the bibliometric viewpoint we can conclude that that there is no reason for condemning self-citations in general or for removing them from macro or meso statistics; supplementary indicators based on self-citations are, nonetheless, useful to understand communication patterns.     

Research performance indicators for university departments: A study of an agricultural university

The present bibliometric study extends previous work by focusing on the research performance of departments in the natural and life sciences, the social and behavioral sciences, and the humanities. The present study covers all 70 departments from one agricultural university, and several veterinary departments of a second university. The impact analysis was extended by including other types of documents than journal articles. For about a third of the departments, publications not covered in citation indexes accounted for at least 30% of the citations to their total oeuvre. To deal with different citation and publication habits in the various fields, both short-term and medium-term impact assessments were made. The commonly used three year window is not universally applicable, as our results show. The inclusion of self-citations forms an important source of error in the ratio of actual/expected impact. To cope with this, the trend and level of self-citations was compared at university level with that in a matched sample of publications. Moreover, at a departmental level, self-citation rates were used to detect departments with divergent levels of self-citation. The expected impact of journals accounted for only 18% of the variance in actual impact. Comparison of bibliometric indicators with two peer evaluations showed that the bibliometric impact analyses provided important additional information.     

Using categorisations of citations when assessing the outcomes from health research

Summary This paper describes an attempt to explore how far a categorisation of citations could be used as part of an assessment of the outcomes from health research. A large-scale project to assess the outcomes from basic, or early clinical, research is being planned, but before proceeding with such a project it was thought important to test and refine the developing methods in a preliminary study. Here we describe the development, and initial application, of one element of the planned methods: an approach to categorising citations with the aim of tracing the impact made by a body of research through several generations of papers. The results from this study contribute to methodological development for the large-scale project by indicating that: only for a small minority of citing papers is the cited paper of considerable importance; the number of times a paper is cited can not be used to indicate the importance of that paper to the articles that cite it; and self-citations could play an important role in facilitating the eventual outcomes achieved from a body of research.     

Detecting <Emphasis Type="Italic">h</Emphasis>-index manipulation through self-citation analysis

The h-index has received an enormous attention for being an indicator that measures the quality of researchers and organizations. We investigate to what degree authors can inflate their h-index through strategic self-citations with the help of a simulation. We extended Burrell’s publication model with a procedure for placing self-citations, following three different strategies: random self-citation, recent self-citations and h-manipulating self-citations. The results show that authors can considerably inflate their h-index through self-citations. We propose the q-index as an indicator for how strategically an author has placed self-citations, and which serves as a tool to detect possible manipulation of the h-index. The results also show that the best strategy for an high h-index is publishing papers that are highly cited by others. The productivity has also a positive effect on the h-index.     

Bibliometrics of a controversial scientific literature: Polywater research, 1962-1974

Summary This study examines the bibliometrics of the controversial scientific literature of Polywater research, focusing on publication types (books, journal publications, conference proceedings, and technical reports). Publication (P) frequency is used to measure publication &ldquo;shape&apos; or pattern and output, citations per publication (CPP) for impact, author self-citations (SC) and uncited publications (UP) for their effect on P and CPP. Findings show an epidemic publication pattern, journal publications with the highest P, books with the highest CPP, and insignificant SC and UP. Comparisons to several non-controversial scientific literatures suggest that these findings may be common to other controversial scientific literatures.     

Publication attributes of leadership: what do they mean?

The article evaluates 48 approaches to leadership for the first time for the period of 1965–2016 using bibliometric methods. Our analysis combines four parameters: the number of publications, citations, self-citations, and dispersion of literature (a new parameter). The question of what is the most influential approach to leadership is addressed. We argue that the interplay among the four attributes observed in this study shows that transformational leadership is the most influential and popular approach to leadership in leadership studies today. However, there is a question of whether the excessive self-citations in this approach to leadership play a role in its augmented visibility.     

Is citation analysis a legitimate evaluation tool?

A comprehensive discussion on the use of citation analysis to rate scientific performance and the controversy surrounding it. The general adverse criticism that citation counts include an excessive number of negative citations (citations to incorrect results worthy of attack), self-citations (citations to the works of the citing authors), and citations to methodological papers is analyzed. Included are a discussion of measurement problems such as counting citations for multiauthored papers, distinguishing between more than one person with the same last name (homographs), and what it is that citation analysis actually measures. It is concluded that as the scientific enterprise becomes larger and more complex, and its role in society more critical, it will become more difficult, expensive and necessary to evaluate and identify the largest contributors. When properly used, citation analysis can introduce a useful measure of objectivity into the evaluation process at relatively low financial cost.Modification of a chapter in E. Garfield:Citation Indexing: Its Theory and Application in Science, Technology and the Humanities, New York, Wiley, 1979.