PhD defence of Nees Jan van Eck on Thursday 13 October 2011

On Thursday 13 October 2011 Nees Jan van Eck will defend his PhD thesis entitled 'Methodological Advances in Bibliometric Mapping of Science'. Supervisors are Professor Rommert Dekker and Dr Jan van den Berg.

Time and location

The PhD defence will take place in the Senate Hall of Erasmus University Rotterdam and will start at 13.30 hrs.

About the PhD thesis

Bibliometric mapping of science is concerned with quantitative methods for visually representing scientific literature based on bibliographic data. Since the first pioneering efforts in the 1970s, a large number of methods and techniques for bibliometric mapping have been proposed and tested. Although this has not resulted in a single generally accepted methodological standard, it did result in a limited set of commonly used methods and techniques.

In this thesis, a new methodology for bibliometric mapping is presented. It is argued that some well-known methods and techniques for bibliometric mapping have serious shortcomings. For instance, the mathematical justification of a number of commonly used normalization methods is criticized, and popular multidimensional-scaling-based approaches for constructing bibliometric maps are shown to suffer from artifacts, especially when working with larger data sets.

The methodology introduced in this thesis aims to provide improved methods and techniques for bibliometric mapping. The thesis contains an extensive mathematical analysis of normalization methods, indicating that the so-called association strength measure has the most satisfactory mathematical properties. The thesis also introduces the VOS technique for constructing bibliometric maps, where VOS stands for visualization of similarities. Compared with well-known multidimensional-scaling-based approaches, the VOS technique is shown to produce more satisfactory maps. In addition to the VOS mapping technique, the thesis also presents the VOS clustering technique. Together, these two techniques provide a unified framework for mapping and clustering. Finally, the VOSviewer software for constructing, displaying, and exploring bibliometric maps is introduced.

About Nees Jan van Eck

Nees Jan van Eck (1982) obtained his master’s degree in Informatics & Economics with honors from Erasmus University Rotterdam in 2005. In the same year, he started his PhD research at the Econometric Institute of the Erasmus School of Economics. Nees Jan’s PhD research is in the field of bibliometrics and scientometrics and focuses on bibliometric mapping of science. Results of his research have been presented at various international conferences and have been published both in bibliometrics/scientometrics journals (Journal of Informetrics, Journal of the American Society for Information Science and Technology, and Scientometrics) and in computer science journals (IEEE Computational Intelligence Magazine and International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems). As part of his PhD research, Nees Jan has developed a computer program for bibliometric mapping called VOSviewer (

Since 2009, Nees Jan has been working as a researcher at the Centre for Science and Technology Studies of Leiden University. He has continued his work on bibliometric mapping of science and on the development of the VOSviewer software, but he has also broadened his interests to other topics in the field of bibliometrics and scientometrics. In 2010, a short research note on one of his bibliometric mapping projects was published in Nature.

See for more information

For more information about this ceremony, please contact the Press Office of Erasmus University Rotterdam phone +31 10 408 1216, email

Publication date: 29 September 2011