Updates and corrections

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

October 9, 2024. Release of the Leiden Ranking Open Edition 2024. This new release of the Leiden Ranking Open Edition is based on the most up-to-date data from the OpenAlex database. In addition, the web interface now offers an easy way to contextualize the ranking statistics by exploring the underlying publications. More information is available in this blog post.

September 20, 2024. We are proud to share that the CWTS Leiden Ranking Open Edition has been nominated and shortlisted for the Leo Waaijers Open Science Award 2024.

July 3, 2024. Release of the 2024 edition of the Leiden Ranking. The number of universities included in the ranking has increased from 1411 to 1506. The following corrections have been made:

• Albert Einstein College of Medicine: additional publications for Albert Einstein College of Medicine have been identified within affiliations mentioning multiple (affiliated) organizations.
• China University of Geosciences: publications from the university with the same name in Beijing that were wrongly attributed to the university in Wuhan have been removed.
• Civil Aviation University of China (CAUC): publications from the Civil Aviation Flight University in China that were inadvertently assigned to this university have been removed.
• Hanoi University of Science and Technology: publications that had been mistakenly assigned to this institution have been removed.
• Heinrich Heine University Düsseldorf: We removed publications from the German Center for Diabetes Research (DZD) that were not from Düsseldorf.
• Inner Mongolia Agricultural University: publications from Inner Mongolia Academy of Agricultural & Animal Husbandry Sciences that were inadvertently assigned to this university have been removed.
• Institut national de la recherche scientifique: additional publications for INRS have been identified within affiliations mentioning multiple (affiliated) organizations.
• Jiangsu University: publications from the Jiangsu University of Science and Technology that were inadvertently assigned to this university have been removed.
• Jiangxi University of Science and Technology: additional publications have been identified that were inadvertently not included before.
• Jilin University: publications from Changchun University of Science and Technology that were inadvertently assigned to this university have been removed.
• Jinan University: publications that appear to belong to University of Jinan assigned to this university have been removed.
• Minia University: additional publications have been identified that were inadvertently not included before.
• Shandong First Medical University: additional publications have been identified that were inadvertently not included before.
• Shanghai University of Finance and Economics: publications from Shanghai University of International Business and Economics that were inadvertently assigned to this university have been removed.
• Tokyo University of Agriculture and Technology: publications from Tokyo University of Agriculture that were inadvertently assigned to this university have been removed.
• Universitat Politècnica de Catalunya - BarcelonaTech: additional publications have been identified for institutions affiliated with UPC.
• Université Cadi Ayyad: additional publications have been identified that were inadvertently not included before.
• Université Côte d'Azur (EPE): additional publications have been identified that were inadvertently not included after the university became an EPE.
• Université du Québec à Montréal: publications from other institutions (e.g. ETS, INRS) within the University of Quebec System have been removed.
• University of Bucharest: additional publications have been identified that were inadvertently not included before.
• University of Caen Normandy: additional publications from Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT) have been identified.
• University of Hawaii, Manoa: Institutes such as Insitute of Astronomy, Cancer Research Center of Hawaii that are part of the University of Hawaii System but not of UH Mānoa have been removed.
• University of Jinan: additional publications have been identified that were previously mistakenly attributed to Jinan University.
• University of Liverpool: publications from the Liverpool School of Tropical Medicine are no longer be automatically considered as output from the University of Liverpool.
• University of North Texas: publications from the Health Science Center in Fort Worth previously included have been removed.
• University of Tennessee, Knoxville: publications from the Health Science Center in Memphis previously included have been removed.
• University of Western Brittany: indicators for University of Western Brittany now include publications of the CHU Brest as the status of this affiliated hospital was revised.
• Xi'An University of Technology: publications from Xi'an Technological University that were wrongly attributed to the university have been removed.

January 30, 2024. CWTS is proud to announce the launch of the Leiden Ranking Open Edition. The Leiden Ranking Open Edition is a fully transparent university ranking based on open data from OpenAlex. More information is available in this blog post.

September 27, 2023. The CWTS Leiden Ranking and the INORMS More Than Our Rank initiative are pleased to announce a new partnership. From now on, the Leiden Ranking highlights universities that support More Than Our Rank. Further information is available in this blog post.

June 21, 2023. Release of the 2023 edition of the Leiden Ranking. The number of universities included in the ranking has increased from 1318 to 1411. More information on the release of the 2023 edition of the Leiden Ranking is available in this blog post.

June 22, 2022. Release of the 2022 edition of the Leiden Ranking. The number of universities included in the ranking has increased from 1225 to 1318.

June 2, 2021. Release of the 2021 edition of the Leiden Ranking. The number of universities included in the ranking has increased from 1176 to 1225. Four new countries have entered the Leiden Ranking with at least one university: Ethiopia, Morocco, Nigeria, and Vietnam. The ranking now includes universities from 69 countries. Some changes have been made to the methodology for the open access indicators. Most importantly, green open access no longer overlaps with the other open access types (i.e., gold, hybrid, and bronze). Green open access now covers only publications that are open access in a repository and not in the journal in which they have appeared.

May 10, 2021. Update of the 2020 edition of the Leiden Ranking. A large number of publications incorrectly were not assigned to Université Grenoble Alpes. These publications have now been assigned to the university and the indicators for the university have been corrected.

August 24, 2020. Update of the 2020 edition of the Leiden Ranking. The following corrections have been made:

• Ritsumeikan University has been added to the ranking. Additional publications have been identified for this university. The publication output of the university now meets the threshold for inclusion in the ranking.
• Japan Advanced Institute of Science and Technology has been removed from the ranking. Some publications were incorrectly assigned to this university. The publication output of the university no longer meets the threshold for inclusion in the ranking.
• Additional publications have been identified for Miguel Hernández University and Osaka Prefecture University. The indicators for these universities have been corrected.

July 9, 2020. Update of the 2020 edition of the Leiden Ranking. Soochow University was incorrectly presented as a university in Taiwan instead of China. This has been corrected.

July 8, 2020. Release of the 2020 edition of the Leiden Ranking. The threshold for a university to be included in the ranking has been reduced from 1000 fractionally counted publications in a four-year time period to 800 fractionally counted publications. As a result, the number of universities included in the ranking has increased from 963 to 1176. Also, some minor improvements have been made to the methodology for determining the gender of an author.

More information on the release of the 2020 edition of the Leiden Ranking is available in this blog post.

July 17, 2019. Update of the 2019 edition of the Leiden Ranking. The following corrections have been made:

• The name of University of Western Sydney has been changed into Western Sydney University.
• Additional publications have been identified for Friedrich-Alexander-Universität Erlangen-Nürnberg, Ulm University, University of Bergen, University of Plymouth, and Western Sydney University. In the case of University of Bergen, publications of the Haukeland University Hospital have been assigned to the university. Previously, these publications were not assigned to the university.
• Some corrections have been made to the data underlying the P(industry) and PP(industry) indicators. As a result, the values of these indicators have decreased for some universities, in particular for North Carolina State University and Duke University.

May 15, 2019. Release of the 2019 edition of the Leiden Ranking. The number of universities included in the ranking has increased from 938 to 963. In addition, the following changes have been made compared with the 2018 edition of the ranking:

• Indicators on open access publishing. Indicators on open access publishing have been added to the Leiden Ranking. Based on Unpaywall data, these indicators provide statistics on the number of open access publications of a university. A distinction is made between gold, hybrid, bronze, and green open access.
• Indicators on gender diversity. Indicators on gender diversity have been added to the Leiden Ranking. These indicators provide statistics on the number of male and female authorships of the publications of a university.

More information on the new indicators included in the 2019 edition of the Leiden Ranking is available in this blog post.

June 14, 2018. Update of the 2018 edition of the Leiden Ranking. The following corrections have been made:

• University of the Chinese Academy of Sciences (UCAS) has been added to the ranking. UCAS is part of the Chinese Academy of Sciences and was originally established as a graduate school in 1978. UCAS received its current name in 2012, and although still focused on postgraduate education, it recently began to enroll undergraduate students. Therefore UCAS has been added to the ranking.
• Sorbonne University in France has been added to the ranking. University Pierre et Marie Curie and University of Paris IV - Paris-Sorbonne have been removed, since they have been merged into Sorbonne University.
• University of Lille in France has been added to the ranking. Lille 1 University has been removed from the ranking, since it has been merged into University of Lille.
• The indicators for University of Bordeaux in France have been corrected. Corrections have been made to the publication data for this university.

May 16, 2018. Release of the 2018 edition of the Leiden Ranking. No major changes have been made to the methodology of the ranking. The criterion for selecting the universities that are included in the ranking has not been changed. The number of universities included in the ranking has increased from 903 to 938. Two new impact indicators have been added to the ranking: P(top 5%) and PP(top 5%).

June 21, 2017. The update of the 2017 edition of the Leiden Ranking that took place on June 19 has led to some minor errors in the indicators for a small number of universities. These errors have been corrected.

June 19, 2017. Update of the 2017 edition of the Leiden Ranking. The following corrections have been made:

• Ulsan National Institute of Science and Technology in South Korea has been added to the ranking. This university incorrectly was not included. As a result of adding this university to the ranking, the total number of universities included in the ranking has increased from 902 to 903.
• The indicators for Norwegian University of Science and Technology have been corrected. The merger with the university colleges of Sør-Trøndelag, Ålesund, and Gjøvik incorrectly had not been taken into account.
• The indicators for Arizona State University in the US have been corrected. Publications from some campuses incorrectly had not been assigned to Arizona State University.
• The indicators for Université Grenoble Alpes in France have been corrected. Some minor corrections have been made to the publication data for this university.

May 17, 2017. Release of the 2017 edition of the Leiden Ranking. The following changes have been made compared with the 2016 edition:

• Indicators on collaboration with industry. These indicators have been reintroduced in the Leiden Ranking. They were available in earlier editions of the ranking, but they were not included in the 2016 edition.
• Fractional counting method. In earlier editions of the Leiden Ranking, address-level fractional counting was used. In the 2017 edition, we have switched to author-level fractional counting. In the case of address-level fractional counting, each address in the address list of a publication has equal weight. In the case of author-level fractional counting, on the other hand, each author of a publication has equal weight. To illustrate the difference between the two fractional counting approaches, consider a publication has been co-authored by five researchers. Three researchers are affiliated with university X. The other two researchers are affiliated with university Y. The three researchers affiliated with university X belong to two different departments within the university. Both departments are listed as a separate address in the publication. The two researchers affiliated with university Y belong to the same department within the university. In the case of address-level fractional counting, used in earlier editions of the Leiden Ranking, the publication is assigned to universities X and Y with weights of 2 / 3 = 0.67 and 1 / 3 = 0.33, respectively. In the case of author-level fractional counting, used in the 2017 edition of the Leiden Ranking, the weights with which the publication is assigned to universities X and Y are, respectively, 3 / 5 = 0.6 and 2 / 5 = 0.4.
• Flemish universities. We have improved the procedure for assigning publications to Flemish universities. The identification of Flemish universities in Web of Science affiliations is particularly difficult because of the name conflation between Flemish and French speaking universities in Belgium. To cope with the complexity of ambiguous affiliations, the Leiden Ranking uses a special assignment procedure for Flemish universities. This procedure is different from the procedure that is used for other universities in the Leiden Ranking. In earlier editions of the Leiden Ranking, we assigned publications to Flemish universities as part of this procedure. In the 2017 edition, we have revised the procedure. Instead of publications, we now assign affiliations within publications to Flemish universities. This influences the weights with which publications are assigned to Flemish universities in the fractional counting approach. In the case of publications with multiple affiliations from the same Flemish university, the weight usually will be higher in the 2017 edition of the Leiden Ranking than in earlier editions. In the fractional counting approach, Flemish universities therefore obtain a substantially larger publication output in the Leiden Ranking 2017 than in earlier editions of the ranking. This provides a more realistic representation of the contribution these universities have made to the publications co-authored by them.

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.