Ludo Waltman

Ludo Waltman is Professor of Quantitative Science Studies at Centre for Science and Technology Studies, Leiden University and Scientific director at Centre for Science and Technology Studies, Leiden University

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CWTS Development

Scholarly communication as a collective responsibility

CWTS has developed a Scholarly Communication Policy that treats publishing as a collective responsibility rather than an individual choice. In this blog post, we introduce the policy, reflect on its co-creation, and invite other institutions to consider adopting a similar approach.

Wolfgang Kaltenbrunner + 2 others • 14-07-2026

Science & Society

Insular policy feedback: Why reforming metrics alone may not be enough

Metric-driven research systems persist because governance structures often matter more than metrics themselves.

Eleonora Dagiene + 3 others • 09-04-2026

CWTS Development · Focal Area: Information & Openness

The CWTS Leiden Ranking 2025 - More open, more inclusive, more informative

The release of the CWTS Leiden Ranking 2025 marks a next step toward more open and more inclusive research analytics for universities. This post highlights the most significant developments.

Nees Jan van Eck + 5 others • 29-10-2025

Focal Area: Information & Openness

Crossref as a source of open bibliographic metadata for preprints

Crossref is a crucial source of open bibliographic metadata for articles published in scientific journals. Importantly, however, Crossref can also serve as a source of bibliographic metadata for preprints. In this post, Van Eck and Waltman analyze the completeness of Crossref’s preprint metadata.

Nees Jan van Eck + 1 other • 16-10-2025

Resources

Making bibliometric reporting more transparent and consistent: Participants needed for pilot testing of GLOBAL

The team behind the GLOBAL reporting guideline invites researchers who are preparing or reviewing a bibliometric article to take part in a pilot test of the guideline.

Jeremy Y. Ng + 4 others • 12-08-2025

Science & Society

The state of preprinting in Europe and the Netherlands

To accelerate the sharing of scientific knowledge, researchers in many disciplines increasingly publish their work on preprint servers. In this post, Ludo Waltman and colleagues discuss the state of preprinting in Europe and the Netherlands.

Ludo Waltman + 2 others • 22-05-2025

CWTS Development · Science & Society

Advancing our Understanding of Systematic Manipulation & Paper Mills: Wiley & CWTS Partnership

The Centre for Science and Technology Studies at Leiden University, in collaboration with the publishing company Wiley, is opening a new position for a PhD candidate to carry out research on paper mills and related forms of systematic manipulation in publishing.

Wolfgang Kaltenbrunner + 4 others • 15-04-2025

Opinion & Commentary

Assessment reform and publishing reform need to go hand in hand

The need to reform research assessment and scientific publishing practices is widely recognized. However, Ludo Waltman argues that the assessment and publishing reform movements will be successful only if they manage to align their agendas.

Ludo Waltman • 26-03-2025

Science & Society

Shaping the Future of Open Research Information - Reflections from the National Open Science Festival

At the National Open Science Festival, we explored challenges in implementing the Barcelona Declaration, including vendor lock-in, data quality, cultural resistance and advocacy gaps. Participants brainstormed actionable solutions, highlighting collaboration, training and outreach as key drivers.

Ana Ranitovic + 2 others • 18-12-2024