Centre for Science and Technology Studies Centre for Science and Technology Studies 2333AL Leiden Zuid Holland 31715273909

Quantitative Science Studies

The Quantitative Science Studies (QSS) research group is one of the three research groups at CWTS. The group is led by Ludo Waltman.


The Quantitative Science Studies (QSS) research group studies science from a quantitative perspective, using methods ranging from mathematical analysis and computer simulation to statistical analysis, network analysis, text mining, and visualization. The focus of the group is on problems in the areas of research evaluation and research management. The QSS group has two main aims. On the one hand, the group aims to make innovative high-quality scientific contributions at the methodological, theoretical and empirical level. On the other hand, the group aims to contribute to the development of improved research evaluation and research management practices. The introduction of a new 'contextualized scientometrics' framework for the use of scientometrics in research evaluation and research management is a key contribution in this area.

Share this page

Research lines

The core areas to which the group intends to contribute are covered by research lines. Each of the research lines is led by a senior member of the group.

Contextualized scientometrics (led by Ludo Waltman)

The contextualized scientometrics research line aims to develop a new framework for the use of scientometrics for supporting research evaluation and research management. Contextualized scientometrics offers an alternative approach to present approaches based on three key principles: context, simplicity, and diversity. According to these principles, scientometric indicators should be complemented with contextual information, they should preferably be simple and easy to understand, and a diversity of scientometric indicators should be made available to cover the different dimensions relevant in the evaluation of scientific research. The research line will use results from a number of other research lines in the QSS group (i.e., altmetrics, bibliometric data sources, full-text analysis, and scientometric tools), and the research line also aims to make use of results from other research groups at CWTS.

Altmetrics (led by Rodrigo Costas)

The main objective of this research line is to investigate the characteristics and possibilities of altmetric data sources in order to provide a more comprehensive and contextualized understanding of science and scholarship. In particular, the research line focuses on the following questions: What is the role of social media in scholarly communication? What could be the value of altmetric data in the framework of contextualized scientometrics? And what are the practical applications of altmetrics for the study of the sciences? To answer these questions, the altmetrics research line takes three main approaches: (1) the conceptual and theoretical study of altmetric data sources and their analytical possibilities, (2) the technical analysis of the features, possibilities, and limitations of altmetric data sources and the metrics they provide, and (3) the development of applications of altmetrics for a variety of practical purposes. The altmetrics research line is expected to develop models of understanding of online activities around scholarly outputs as well as practical proposals on how these models can be framed in research evaluation and scientometric studies.

Data sources (led by Nees Jan van Eck)

This research line is concerned with analyzing and comparing the characteristics of different data sources for bibliometric analysis, such as Web of Science, Scopus, Dimensions, Microsoft Academic, Crossref, and OpenCitations. The research line focuses on performing in-depth comparisons of data sources and on analyzing the way in which differences between data sources affect the outcomes of bibliometric analyses. The research line also studies data sources that provide access to the full text of scientific publications.

Modelling the research system (led by Vincent Traag)

This research line focuses on building quantitative models of the research system and on analyzing these models mathematically and by using computer simulations. The models constructed in the research line aim to provide an enhanced understanding of the way in which the system works. Moreover, they aim to offer a deeper insight into possible improvements that can be made to the system. These improvements could address all kinds of issues that are commonly perceived as problematic in today’s research system, such as funding being overly competitive, review and evaluation taking too much time, and many studies not being replicable. Specifically, our modelling research line aims to focus on the following three topics: (1) funding and strategic behavior, (2) open science, and (3) knowledge accumulation. Models will be grounded in careful theoretical reasoning, but will also be based on empirical insights, both from large-scale quantitative data sources and from qualitative lab studies and fieldwork.

Networks (led by Vincent Traag)

The key elements of scientometric data sets often can be conveniently represented as networks. In the networks research line, we study scientometric networks, with a special focus on the development of techniques and algorithms for analyzing these networks. A focal area of interest is clustering of large networks, where we have for instance developed the Leiden algorithm. Another important area is the visualization of networks. Finally, a network perspective is crucial in understanding the diffusion of scientific knowledge. We are particularly interested in developing techniques for studying knowledge diffusion based on citation networks.

Scientometric tools (led by Nees Jan van Eck)

VOSviewer and CitNetExplorer are two popular freely available scientometric software tools developed at CWTS. The scientometric tools research line aims to continue the development of these tools and the underlying algorithms. In particular, the research line aims to develop a completely new version 2.0 of the VOSviewer tool for visualizing bibliometric networks. VOSviewer 2.0 will be able to handle very large networks and will support innovative ‘drill-down’ functionality for exploring these networks. It is expected that VOSviewer 2.0 will also play an important role in implementing the idea of contextualized scientometrics.


For more information about the QSS research group, please contact Ludo Waltman

Group members

Juan Pablo Bascur Cifuentes

PhD candidate and member of the QSS research group. His research focuses on machine learning and natural language processing of papers to improve literature searches.

Giovanni Colavizza

Visiting researcher focusing on full-text analytics and the humanities. Giovanni is interested in computational approaches to model the use scholars make of language, in science within Wikipedia, and in understanding the social and intellectual organisation of humanities disciplines.

Rodrigo Costas

Senior researcher. Rodrigo's research focuses on the development of new social media metrics (altmetrics), new scientometric applications at the individual-level and the study of funding acknowledgements.

Nees Jan van Eck

Senior researcher, head of data science, and coordinator of the Information & Openness focal area. Nees Jan's research focuses on infrastructures and the development of tools and algorithms to support research assessment, science policy, and scholarly communication.

Zhichao Fang

Visiting researcher. Zhichao’s research interests focus on the development and application of altmetrics and usage metrics.

Kwun Hang (Adrian) Lai

PhD candidate of the Quantitative Science Studies research group at the Centre for Science and Technology Studies (CWTS)

Wout Lamers

PhD candidate also affiliated with the Leiden Centre of Data Science. Wout’s research focuses on studying patterns in scientific knowledge accumulation using full-text analysis of publications.

Tina Nane

Visiting researcher. Tina's research focuses on the statistical analysis and modeling of bibliometric data and citation networks.

Vincent Traag

Senior researcher and bibliometric consultant. Vincent's research focuses on complex networks and social dynamics. He holds a Master in sociology and a PhD in applied mathematics, and tries to combine the two in his work.

Martijn Visser

Researcher and PhD candidate. Martijn's research focuses on data sources for the measurement of research performance.

Ludo Waltman

Ludo Waltman is professor of Quantitative Science Studies and scientific director at the Centre for Science and Technology Studies (CWTS) at Leiden University. He is a coordinator of the Information & Openness focal area and a member of the Evaluation & Culture focal area. Ludo is co-chair of the Research on Research Institute (RoRI).

Jian Wang

Assistant Professor at the Science Based Business Program, Faculty of Science, Leiden University.  

Zohreh Zahedi

Visiting researcher and member of Quantitative Science Studies research group. Zohreh’s research focuses on studying the interactions between social media and science (Social Media Study of Science)

Build on Applepie CMS by Waltman Development