The bibliometric results in Vipunen are based on two publication databases, Web of Science (abbreviated WoS) and Scopus. WoS from Clarivate Analytics derives from the Science Citation Index by Eugene Garfield in the 1960s (Chadegani et al. 2013). Being the oldest citation database, WoS Collection dates back to 1900. Scopus was created in 2004 by the Dutch publishing company Elsevier. While it has a shorter time coverage than WoS, many studies have noted that Scopus provides a higher coverage of scientific publications (Vieira & Gomes 2009; Haddow & Genoni 2010; Pranckutė 2021). Moreover, the coverage in databases varies between scientific fields with some represented more than others (Pranckutė 2021). WoS is composed of a variety of indexes while content in Scopus is more integrated (Pranckutė 2021). As such, WoS Core Collection includes several main citation indexes: Science Citation Index Expanded (SCIE); Social Sciences Citation Index (SSCI); Arts & Humanities Citation Index (A&HCI); Conference Proceedings Citation Indexes (CPCI-S, CPCI-SSH); Books Citation Indexes (BKCI-S, BKCI-SSH). The results in Vipunen are also partly based on the WoS Emerging Sources Citation Index (ESCI).. While the Emerging Sources Citation Index has been added to WoS and the coverage of non-English publications expanded, some researchers argue that Scopus still outperforms WoS in regional coverage (Pranckutė 2021).
In Table 1, we show the number of scientific publications with at least one researcher with a Finnish affiliation for both databases. As can be seen, these sources are more or less equally complete (or lacking) in their coverage of Finnish publications. For comparison, we have presented the corresponding figures from Research.fi, which contains publication data only from Finnish higher education institutions and most government research institutes. The amount of scientific publications in the commercial databases is annually only roughly 2/3 of the volume of Research.fi.
| Number of Publications | Web of Science (CORE + ESCI) | Scopus | Research.fi |
| 2017 | 18 893 | 18 012 | 28 791 |
| 2018 | 19 184 | 19 263 | 29 084 |
| 2019 | 19 937 | 20 546 | 29 823 |
| 2020 | 19 866 | 20 740 | 30 069 |
As can be seen from Figure 1 below, Scopus appears to include clearly more Finnish scientific papers than WoS (CORE collection). However, any comparison between subject fields is complicated by the fact that, on average, the publications are assigned more subject fields in Scopus than in WoS. Thus, a publication can represent just, say, Biosciences in WoS, but both Biosciences and Medical Sciences in Scopus. This leads to at first sight somewhat paradoxical situations, where the number of Scopus indexed publications in Biosciences which are also included in WoS (the lighter part of the Scopus column) is larger than the total number of publications classified as Biosciences in WoS (the whole blue column)
In all fields, Scopus has a slightly larger share of publications indexed in only one of the two databases. The situation becomes more balanced with the inclusion of WoS ESCI (Emerging Sources Citation Index) publication data.
For measuring the scientific impact of any given set of publications, currently the most used indicator is the Top10 index, which tells how large share of the publications in the focal set belong to the most cited 10% in their respective subject fields when compared with other publications of equal age.
In country-level analyses WoS-based and Scopus-based data offer a very similar picture of the quality of research as assessed using the Top10 index. Analyses based on fields of science yield somewhat different results, because of the differences in database coverage. There are also some differences in fields of science classifications. (Suomen Akatemia 2021)
A Table below presents Top10 citation index for Finland for two recent 4-year periods: 2015-2018 and 2016-2019. For Finnish publications, values of the indicator tend to be higher for all main scientific fields for Scopus data as compared to WoS data (except the Other category which may be differently composed in databases). This phenomenon does not hold in general for all countries, years or subject fields; e.g., for China the WoS data usually yields clearly higher indicator values than Scopus data. A more refined subject field classification would also reveal that, for example, in Genetics and the Agricultural Sciences WoS results in higher impact values for Finnish publications than Scopus. The single most significant factor behind these differences is the larger share of publications written in other languages than English in Scopus.
Table 2. Comparison of Top10 index for Finnish publications in WoS and Scopus in 2015-2018, 2016-2019.
Table 2 does not show any indicator value for the Humanities in Web of Science. This is not due to lack of publications, but the reason is low internal coverage. The number of publications in these databases varies strongly between main fields of science. In particular, non-English publications from Social Sciences and Humanities fields are poorly represented. Therefore the number of publications does not accurately reflect the true extent of scientific publishing or citation patterns in these fields. Formulated in a more specific manner, we look at how large share of all sources listed in all publications are also indexed in the same database. This percentage is called the internal coverage, and it’s customary not to report citation impact for any fields where this figure is below 40%. For a much better coverage of Finnish publications in the Humanities, see Research.fi.
Vipunen reports also allow comparison by organization types. In general, the numbers of publications are close to one another in WoS and Scopus.
Data source: Vipunen.fi.
The differences between the databases and the results calculated based on these highlight the fact that bibliometrics does not offer universal truths. Bibliometrics is one way of depicting the volume and scientific impact of research. Analysing large enough entities (e.g., countries, fields of science) and trends rather than individual years as well as combining bibliometrics with peer review helps in drawing a more holistic picture of the reseach landscape.
References:
Chadegani, A. A., Salehi, H., Yunus, M. M., Farhadi, H., Fooladi, M., Farhadi, M., & Ebrahim, N. A. (2013). A comparison between two main academic literature collections: Web of Science and Scopus databases. arXiv preprint arXiv:1305.0377.
Haddow, G., & Genoni, P. (2010). Citation analysis and peer ranking of Australian social science journals. Scientometrics, 85(2), 471-487.
Pranckutė, R. (2021). Web of Science (WoS) and Scopus: The titans of bibliographic information in today’s academic world. Publications, 9(1), 12.
Suomen Akatemia (2021). Tieteen tila-tilastot: Scopus- ja Web of Science -tietokantojen eroista.
Vieira, E., & Gomes, J. (2009). A comparison of Scopus and Web of Science for a typical university. Scientometrics, 81(2), 587-600.
Text by Valeria Caras, edited by Yrjö Leino
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