Note: Should you found this article online, please quote my work, will you?
- General Information about h-Index
H-index is a bibliometric measure that was introduced by Jorge Hirsch in August 2005 (Hirsch, 2005a, 2005b). It is defined as “a scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np – h) papers have no more than h citations each” (Hirsch, 2005, p. 16569). In a simpler explanation, h-index project the strength of a scholar or scientist work based on the set of the person(s) most cited papers and the number of citations that they have received in other publications. Thus, h-index measures individual scholarly performance in the term of productivity and citation impact of the publication through the author-level metric.
Why h-index is important for scholars and researchers? Because h-index represents as a standard tool to measure the scientific publication output of the researcher in term of quality and quantity. H-index will specifically address the issues of self-citation, original research contribution, favourism and etc. It is an author-level metrics to explicitly measure the impact of the individual authors, researcher, academics and scholars. The value differs from one field to another, as it is highly affected by based on the discipline citation database, publication, ranges of years and etc. Hence, a low number of h-index that is considered low in one field might be considered quite high in another field.
Another purpose of the h-index is to eliminate outlier publications that might give a skewed picture of a scientist’s impact. For instance, if a scientist published one paper many years ago and it has been cited 8546 times, but has since only published papers that have been cited 8 or 9 times each, a straight citation count for that scientist could make it seem that his or her long-term career work was very significant (Nina Diana, 2020).
The h-index platform of Web of Science, Scopus and Google Scholar has their unique strengths as well as their disadvantages. The discussion is segmented under 5 topics which are explained in details below:
- a) The availability of the H-index provider
Web of Science and Scopus: are only available to those academics whose institutions are able and willing to bear the (quite substantial) subscription costs of the Web of Science and other databases in the Thomson ISI Web of Knowledge. This also occurs to Sopus (Harzing, 2010)
Google Scholar is freely available to anyone with an Internet connection and is generally praised for its speed (Bosman et al. 2006).
Scholars indicate “that, free access to data provided by Google Scholar provides an avenue for more transparency in tenure reviews, funding and other science policy issues, as it allows citation counts, and analyses based thereon, to be performed and duplicated by anyone. Another compared citation counts from Google Scholar to the research output from universities under New Zealand’s PBRF (Performance Based Research Funding) research assessment exercise and found a very high (0.94) correlation between the PBRF output (defined as PBRF quality score times the FTE staff size) and the total number of citations returned by Google Scholar (Harzing, 2020)
- b) The comprehensiveness of citation coverage to measure h-index
Web of Science (WOS) : Citation is backdated to the year of 1961 onwards. The original source is Science Citation Index. WOS claims that their citation references has reached 1.5 billion cited references dating back to 1900. WOS counts exact matches only. It doesn’t count multiple manifestation of a work.
Scopus : It is launched in November 3, 2004. The full citation coverage is from 1996 onwards. Over the years, Scopus has added 195 million more cited references, dating back to 1970. The database’s existing records also claim that it has captured as far a dated back to 1788 and has since further increased the depth of content. However, SCOPUS provides citation data only for the items indexed by it (Bar-Ilan, J.,2008)
Google Scholar (GS): Launched in November 18, 2004. GS freely indexed anything it can compile. It is estimated to house about 389 million records, ranging from GS indexes non-scholarly sources as well. Often, GS indexes both the preprint and the journal version of a paper.
Scopus and WOS have distinguish and distinctive way of handling the collected publications. Scopus has the advantages of higher citation measurement due to the extent of its field coverage in Physical sciences, health sciences, life sciences, social sciences & humanities. Whilst WOS has more historical depth as compared to Scopus and focuses more on the Science, technology, social sciences, arts and humanities. Therefore, WOS has the advantages of providing legit citation references and projects superiority as it covers older publications compared to Scopus and Google Scholar (GS) (Bar-Ilan, J.,2008)
However, WOS counts exact matches compare to GS. GS has the advantages of providing more comprehensive citation as it also covers materials that is not covered by WOS and SCOPUS, examples, books, conference papers, working papers and student theses. But, GS mechanism of citation tracker has raises the issue of multiple manifestations of a work. As it allows automated tracking GS has the ability to harvest any citation found as it is not subject to any review. On one hand, it provides higher citation counts for the authors, on the other hand, the citation may be manipulated. Whereas, Scopus has built a reputation in providing better coverage towards the subject covered lesser in WOS, especially in the field of Social Science studies.
Authenticity of the citation sources
(i) Web of Science: Before 2004, WOS is the only comprehensive database that provides citation counts . The citation is originally from Science Citation Index. It is governed under the jurisdiction of the Institute for Scientific Information, (ISI). ISI is the institution that developed and produced the Science Citation Index (SCI), Social Sciences Citation Index (SSCI), and the Arts and Humanities Citation Index (AHCI). The basic principles of the WOS selection process consist of objectivity, selectivity and collection dynamics. WOS have about 28 criteria used to evaluate journals.
(ii) Scopus : It reported broader overview of interdisciplinary scientific data and literature, across all research areas. Scopus is also governed by the Scopus Content Selection and Advisory Board (CSAB), an international group of scientists, researchers and librarians who represent the major scientific disciplines to ensure that the high-quality and authenticity of the published articles.
(iii) Google Scholar : is a freely indexed publication and to the best knowledge of the author, it has not declared any specific advisors or governing bodies to ensure the quality of its citation sources (Bar-Ilan, J.,2008)
The fundamental formula of h-index is highly depending on the number of publications and the number of citations per publication. Therefore, the h-index of one same author can be projected differently between Google Scholars (GS), Scopus (S) and Web of Science (WOS) due to the source of publication database, focus area, the maturity and others. As each feature has its own distinctive database, eventually each platform will exhibit different value of h-index.
Scopus and WOS have a systematic reviewer while it is unclear about the GS team of reviewers. Google Scholar also doesn’t provide any explicit information neither about the number of records nor about its timely coverage. Google index data from publishers only if the publisher is willing to provide at least the abstract of the paper freely or freely accessible. It is unfortunate that dishonesty may occurred among researcher as they could simply upload false scholarly papers that give unsupported citation credit, or add papers to the Google Scholar profile that were not even authored by the person in question.
Somehow, Google Scholars is more up to date, as their h-index includes the citations before the articles officially published. Whereas Scopus is a very useful alternative for measuring the citation impact of articles, journals and authors. It also covers a larger dataset, so more articles, journals and conference papers will have metrics as well as a citation. And WOS has stronger jurisdiction as it is developed from ISI, a world prestigious organization with scientific information and a long tradition in publications’ tracking.
Citation of Non-English publication sources
(i) Web of Science : traditionally, it is based upon English based publications and covers mostly the publication from the Western region especially from the USA and British.
(ii) Scopus : has been known to be supportive towards non-spoken English regions such as the Asia and the Middle East. To a certain extend, Scopus does allow the viewing of other languages in their databases, for example, Malay, Chinese and Arabic languages.
(iii) Google Scholar: any publication that allows its publications to be tracked by GS tracking robots.
Harzing (2010) indicates that The Web of Science includes only a very limited number of journals in languages other than English (LOTE) and hence citations in non-English journals are generally not included in any Web of Science citation analysis. Noruzi (2005) in Harzing (2008) mentioned that Google Scholar’s LOTE coverage includes a larger number of publications in other languages and indexes documents such as French, German, Spanish, Italian and Portuguese. Meho & Yang (2007) in Harzing (2008) reported that 6.94% of Google Scholar citations were from LOTE, and only 1.14% coverage of the Web of Science and 0.70% for Scopus.
Higher error in citations is subject to many forms of error as it can occur from typographical errors in the source paper to analytical errors. From Harzing (2020) analysis, Google Scholar is subject to have a higher occurrence in error, from the parsing of the reference, to errors due to some nonstandard reference formats. Scholars have claimed that Google Scholar reports higher citation counts for certain disciplines. However, all three providers may have difficulties in treating publications such as books or conference proceedings are inconsistent. This resulted that the citations to the works can be completed, completely missing, or anywhere in between.
Finally, it is also worth mentioned that, all the three providers had similar issues in providing a consistent set of author abbreviations (names with diacritics or apostrophes; names with ligatures and non English names such as Malays and Arabics names).
The author’s choice of H-Index
My disciplines coverage focuses to the field of Social Sciences. From the comparative discussion of h-index providers between Web of Science, SCOPUS and Google Scholars, I am more interested to employ Scopus h-index to monitor my publication’s impact. Though Google Scholar mentioned that it has the ability to find most of the citations to Social Sciences articles by 94%, while Web of Science and Scopus only covers 35% and 43%, Scopus has consistently provides wider coverage, especially for Social Science disciplines. Moreover, though Web of Science presents most authoritative source, Scopus is a more useful alternative for measuring the citation impact of articles, journals and authors as it covers larger data set, especially towards the Social Science publication.
Compared to WOS, Scopus has indexed more publication in a Social Science related field and Scopus does have the authoritative body to monitor its content authenticity. Scopus projects broader overview of interdisciplinary scientific data and literature, across all research areas. Scopus is also governed by the Scopus Content Selection and Advisory Board (CSAB), an international group of scientists, researchers and librarians who represent the major scientific disciplines to ensure that the high-quality and authenticity of the published articles. Therefore, the Scopus h – index has the capability of measuring an academician whole body of work and gives the scholar a better evaluation of his or her work.
In general, WOS and SCOPUS provide an almost similar set of citation counts. Thus, this affirmed my believe that the citation calculation provided by Scopus is also as thorough and meticulous as the publications based on WOS. Though Google Scholar has an automated capability to crawl through non-scholarly sources and project highest citation score, its credibility is still being questioned as GS does not have specific governing bodies that monitor the authenticity of its content.
Another reason is, Scopus does cover wider publication in non-English written materials. This initiative has proven to balance the current weighing of scholarly indicators that has the propensity towards Western knowledge dissemination comparison to the other parts of the world. Moreover, this initiative motivates researchers to share their current work with the locals so the general public has the opportunity to read and learn about current research work. And it is my wish that the findings may finally impact the benefits of the nation and the building of the nation itself.
Somehow, Google Scholar (GS) is another convenient platform to introduce others about my current work and citation. Nevertheless, the authenticity, reliability and integrity of GS source and the mechanism can still be questioned as it doesn’t belong to any controlled group or committee. Finally, by positioning my scholarly work to h-index measurement, it surely assists my publications’ performance progress, project impactful recognition towards my scholarly work and better projection of my research work’s reputation.
Bar-Ilan, J. (2008). Which h-index?A comparison of WoS, Scopus and Google Scholar. Scientometrics,74(2).page 257-271.
- Hirsch (2005). An index to Quantify an Individual’s Scientific Output. Proceedings of the National Academy of Sciences of the United States of America, 102 (2005) 16569–16572
Harzing, A. W. (2010). Google Scholar-a new data source for citation analysis. online] URL: http://www. harzing. com/pop_gs htm. Accessed, 22(12), 2010.
Nina Diana Nawi (2020). The difference between h-index in Google scholar, SCOPUS and Web of Science. People@UTM website.
Web of Science Journal Evaluation Process and Selection Criteria. Retrieved from https://clarivate.com/webofsciencegroup/journal-evaluation-process-and-selection-criteria/
LibGuides: Web of Science platform: Web of Science Core Collection. Retrieved from https://clarivate.libguides.com/webofscienceplatform/woscc