Updates and corrections

The following updates and corrections have been made to the CWTS Leiden Ranking.

May 18, 2016. Release of the 2016 edition of the Leiden Ranking. The following changes have been made compared with the 2015 edition:

  • Selection of universities included in ranking. In the 2015 edition of the Leiden Ranking, the 750 universities worldwide with the largest Web of Science indexed publication output were included. In the 2016 edition, we use a different approach to select the universities that are included in the ranking. Rather than selecting a fixed number of universities, we include all universities worldwide whose publication output is above a fixed threshold. This threshold equals 1000 fractionally counted Web of Science core publications in the period 2011–2014. Using this threshold, 842 universities have been selected for inclusion in the 2016 edition.
  • Academic hospitals. The treatment of some academic hospitals has changed in the 2016 edition of the Leiden Ranking. In earlier editions, publications mentioning an affiliation with an academic hospital that is part of or controlled by a university were assigned to the university. In addition, publications from an academic health science center to which a university delegates its medical research and teaching duties were also assigned to the university. In the 2016 edition, publications from academic hospitals that do not satisfy the above criteria but that are nevertheless very tightly integrated with a university are also assigned to the university. Researchers that work at these hospitals but that are employed by the university often turn out not to mention their affiliation with the university. We assume that researchers do not mention their university affiliation because the hospital is perceived to be part of the medical faculty of the university.
  • Inter-institutional collaboration indicators. In the 2015 edition of the Leiden Ranking, a collaboration between a university and an affiliated organization that is considered to be part of the university was regarded as an inter-institutional collaboration. For instance, a collaboration between Leiden University and Leiden University Medical Center was seen as an inter-institutional collaboration. In the 2016 edition, these collaborations are no longer regarded as inter-institutional collaborations.
  • International collaboration indicators. In the 2015 edition of the Leiden Ranking, England, Northern Ireland, Scotland, and Wales were regarded as separate countries in the calculation of the international collaboration indicators. In the 2016 edition, the United Kingdom is regarded as a single country in the calculation of the international collaboration indicators. Hence, a collaboration between for instance an English and a Scottish university is no longer seen as an international collaboration.
  • Indicators on collaboration with industry. These indicators are no longer available in the Leiden Ranking. Indicators on universities’ collaboration with industry will be published separately in 2017.
  • Website. The Leiden Ranking website has been significantly revised. In addition to a traditional list-based presentation, where universities are presented in a list ranked based on a selected indicator, the revised website also offers a chart-based and a map-based presentation. Furthermore, in the list-based presentation on the revised website, size-dependent and size-independent indicators are always presented together and the P indicator has replaced the PP(top 10%) indicator as the default indicator for ranking universities.

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