2015 Google Scholar Metrics released
WHAT IS NEW IN GOOGLE SCHOLAR METRICS 2015?
No surprises. Almost with the punctuality of a fine Swiss watch, Google released, on Thursday, June 25th, 2015, 12:16 PM, its ranking of scientific publications: Google Scholar Metrics (GSM). Last year’s version was published a one month before, on Thursday, June 26, 2014,5:24 PM. Google has stopped being different: it seems that from now on, these coveted lists of publications sorted by their scientific impact (that is, their h index) will be released every. This means that GSM: Google Scholar Metrics will join it competitor (JCR:Journal Citation Reports) in updating the product on a yearly basis: JCR 2015 appeared last week.
We can only welcome that the American company has decided to keep supporting GSM, a free product which is also very different from traditional journal rankings. Competition is healthy, and scientists can only be pleased about this variety of search and ranking tools, especially when they are offered free of charge.
Continuity and stability are the norm in this edition. The total number of publications that can be visualized in the 2015 rankings is 7,211. Now, however, since 1,761 of them (24.2%) are classified in more than one subject area, the number of unique publications is lower: 5,450.
In short, Google has just updated the data, which means that some of the limitations outlined in previous studies still persist [1-5]: the visualization of a limited number of publications (100 for those that are not published in English), the lack of categorization by subject areas and disciplines for non-English publications, and normalization problems (unification of journal titles, problems in the linking of documents, and problems in the search and retrieval of publication titles). As an example, it is inexcusable that there are duplicates to be found in a ranking of the top 100 publications (according to their h5-index) of a particular language. This is the case with the journal Íconos-Revista de Ciencias Sociales, which appears in the 99nd and 100th positions in the spanish rankings (have been rectified now); but in honor of the truth, errors are lower than in previous years.
In our previous studies, we have described again and again the underlying philosophy embedded in all of Google’s academic products. These products have been created in the image and likeness of Google’s general search engine: fast, simple, easy to use, understand and calculate?, and last but not least, accessible to everyone free of charge. GSM follows all these precepts, and it is, in the end, nothing more than:
- A hybrid between a bibliometric tool (indicators based on citation counts), and a bibliography (a list of highly cited documents, and of the documents that cite them).
- It offers a simple, straightforward journal classification scheme (although it also includes some conferences and repositories).
- It is based on two basic bibliometric indicators (the h index, and the median number of citations for the articles that make up the h index).
- It covers a single five-year time frame (the current one being 2010-2014).
- It uses rudimentary journal inclusion criteria, namely: publishing at least 100 articles during the last five-year period, and having received at least one citation.
- It provides lists of publications according to the language their documents are written in. For all of them, except for English publications (these are a total of 8: Chinese, Portuguese, German, Spanish, French, Japanese, Dutch, and Italian) it offers lists of only 100 titles: those with the higher h index. For English publications, however, it shows a total of 4655 different publications, grouped in 8 subject areas. For each publication, it shows the titles of the documents whose citations contribute to the h index, and for each one of these documents, in turn, the titles of the documents that cite them.
- It provides a search feature that, for any given set of keywords, will retrieve a list of 20 publications whose titles contain the selected keywords. In the cases where there are more than 20 publications that satisfy the query, only the first 20 results, those with a higher h index, will be displayed.
- It doesn’t perform any kind of quality control in the indexing process nor in the information visualization process.
To sum up, GSM is a minimalist information product with few features, closed (it cannot be customized by the user), and simple (navigating it only takes a few clicks). If GSM wants to improve as a bibliometric toolit should incorporate a wider range of features. At the very least, it should:
- Display the total number of publications indexed in GSM, as well as their countries and language of publication. Our estimations lead us to believe that this figure is probably higher than 40,000 . In the case of Spain, there are over 1,000 publications indexed, which make up about 45% of the total number of academic publications in Spain [7-9].
- Provide some other basic and descriptive bibliometric indicators, like the total number of documents published in the publications indexed in GSM, and the total number of citations received in the analysed time frame. These are the two essential parameters that make it possible to assess the reliability and accuracy of any bibliometric indicator. Other indicators could be added in order to elucidate other issues like self-citation rates, impact over time (immediacy index), or to normalize results (citation average).
- Provide the complete list of documents of any given publication that have received n citations and especially those that have received 0 citations. This would allow us to verify the accuracy of the information provided by this product. It is true, much to Google’s credit, that this information could be extracted, though not easily?, from Google Scholar.
- Provide a detailed list of the conferences and repositories included in the product. The statement Google makes about including some conferences in the Engineering & Computer Science area, and some document collections like the mega-repositories arXiv, RePec and SSRN, is much too vague.
- Define the criteria that has been followed for the creation of the classification scheme (areas and disciplines), and the rules and procedures followed when assigning publications to these areas and disciplines.
- Enable the selection of different time frames for the calculation of indicators and the visualization and sorting of publications. The significant disparities in publishing processes and citation habits between areas (publishing speed, pace of obsolescence) require the possibility to customize the time frame according to the particularities of any given subject area.
- Enable access to previous versions of Google Scholar Metrics (2007-2011, 2008-2012, 2009-2013) to ensure that it is possible to assess the evolution of publications over time. Moreover, they could dare venture into the unknown and do something no one else has done before: a dynamic product, with indicators and rankings updated in real-time, just as Google Scholar does.
- Enable browsing publications by language, country and discipline, and directly display all results for these selections.
- Remove visualization restrictions: currently 100 results for each language and 20 for each discipline or keyword search.
- Enable the visualization of results by country of publication and by publisher.
- Enable sorting results according to various criteria (publication title, country, language, publishers), as well as according to other indicators (h index, h median, number of documents per publication, number of citations, self-citation rate…).
- Enable searching not only by publication title, but also by country and language of publication.
- Enable an option for exporting global results, as well as results by discipline, or those of a custom query.
- Enable an option for reporting errors detected by users, so they can be fixed (duplicate titles, erroneous titles, incorrect links, deficient calculations…).
Dixit a year ago
Isolated errors we've found in this edition:
- Missing journals: the journal Ars Pharmaceutica is missing from this year's edition. However, from several queries on Google Scholar (1, 2) we see that this journal meets the requirement of having published at least 100 documents in the period of evaluation (2010-2014), and having received at least one citation. Moreover, there is a public Citations Profile available for this journal.
- Misattributions: many documents published in "Revista Interuniversitaria de Formación del Profesorado" have been misattributed to the journal "Nómadas. Revista Crítica de Ciencias Sociales y Jurídicas".
- It includes incorrectly Área abierta, which published 78 papers in 2010-2014, well below the 100 required for indexing GSM. Besides, miscalculated its index h by not including his most cited article in 2010-2014: Jóvenes, ficción televisiva y nuevas tecnologías with 20 cites
- New duplicate titles journals: Revista Rol de Enfermería = Revista de enfermeria (Barcelona, Spain).
1. Delgado López-Cózar, E; Cabezas-Clavijo, Á (2012). Google Scholar Metrics updated: Now it begins to get serious. EC3 Working Papers 8: 16 de noviembr de 2012. Available: http://digibug.ugr.es/bitstream/10481/22439/6/Google%20Scholar%20Metrics%20updated.pdf
2. Delgado-López-Cózar, E., y Cabezas-Clavijo, Á. (2012). Google Scholar Metrics: an unreliable tool for assessing scientific journals.El Profesional de la Información, 21(4), 419–427. Available: http://dx.doi.org/10.3145/epi.2012.jul.15
3.Cabezas-Clavijo, Á., y Delgado-López-Cózar, E. (2012). Scholar Metrics: el impacto de las revistas según Google, ¿un divertimento o un producto científico aceptable? EC3 Working Papers, (1). Available: http://eprints.rclis.org/16830/1/Google%20Scholar%20Metrics.pdf
4. Cabezas-Clavijo, Álvaro; Delgado López-Cózar, Emilio (2013). Google Scholar Metrics 2013: nothing new under the sun. EC3 Working Papers, 12: 25 de julio de 2013. Available: http://arxiv.org/ftp/arxiv/papers/1307/1307.6941.pdf
5. Martín-Martín, A.; Ayllón, J.M.; Orduña-Malea, E.; Delgado López-Cózar, E. (2014). Google Scholar Metrics 2014: a low cost bibliometric tool. EC3 Working Papers, 17: 8 July 2014. http://arxiv.org/pdf/1407.2827
6. Delgado López-Cózar, E.; Cabezas Clavijo, A. (2013). Ranking journals: could Google Scholar Metrics be an alternative to Journal Citation Reports and Scimago Journal Rank? Learned Publishing, 26 (2): 101-113. Available: http://arxiv.org/ftp/arxiv/papers/1303/1303.5870.pdf
7. Delgado López-Cózar, E.; Ayllón, JM, Ruiz-Pérez, R. (2013). Índice H de las revistas científicas españolas según Google Scholar Metrics (2007-2011). 2ª edición. EC3 Informes, 3: 9 de abril de 2013. Available: http://digibug.ugr.es/handle/10481/24141
8. Ayllón Millán, J.M.; Ruiz-Pérez, R.; Delgado López-Cózar, E. Índice H de las revistas científicas españolas según Google Scholar Metrics (2008-2012). EC3 Reports, 7 (2013). Available: http://hdl.handle.net/10481/29348
9. Ayllón, Juan Manuel; Martín-Martín, Alberto; Orduña-Malea, Enrique; Ruiz Pérez, Rafael ; Delgado López-Cózar, Emilio (2014). Índice H de las revistas científicas españolas según Google Scholar Metrics (2009-2013). EC3 Reports, 17. Granada, 28 de julio de 2014. Available: http://hdl.handle.net/10481/32471
Granada, June 26, 2015, 22:10 PM.