10. Measuring Science: Basic Principles and Application of Advanced Bibliometrics

We begin with a short history of measuring science and discuss how the Science Citation Index has revolutionized the quantitative study of science and created a strong application potential. After reviewing the rationale of bibliometric analysis, we present the basic principle of the bibliometric methodology, with complex citation networks as a starting point. We show that the two main pillars of advanced bibliometric methods, citation-based analysis and science mapping, are both reducible to one and the same principle. From this basic principle we deduce a set of main indicators, particularly for the assessment of research output and international impact. Important elements include new approaches for identifying fields and research themes on the basis of a publication-level rather than a journal-level network; publication and citation counting; normalization of citation measures; the use of indicators based on averages versus those based on citation distributions; and weighting procedures and statistical reliability. In this account of the state of the art of advanced bibliometrics, we highlight in particular the developments in our Leiden institute, given its long-standing, extensive, and broad experience.

The next part of this chapter deals with practical applications of indicators, particularly real-life examples of evaluation studies. We further discuss several crucial issues such as the use of journal impact factors and h-index; the relation between peer review judgment and bibliometric findings; definition and delimitation of fields; assignment of publications; the influence of open access; webometrics and altmetrics; ranking of universities; and general objections to bibliometric analysis.

The second main pillar of the advanced bibliometric methodology is the development of science maps. We discuss the basic elements and the construction of both citation-relation and word-relation science maps. Further, we present a method to combine the two main pillars: the integration of citation analysis in science maps. This combined citation analysis and science mapping can be used to explore research related to socioeconomic problems. Recently developed bibliometric instruments enable tunable mapping, which opens up new analytical opportunities in monitoring scientific research. Finally, we contend that bibliometric indicators and maps are not just evaluation tools for science policymakers, research managers, and individual researchers, but also powerful instruments in the study of science.