1. Introduction1
The goal of this study is to develop a comprehensive indicator of integration among countries
within a supranational system. The main novelty incorporated in the indicator proposed here
holds that an integration process among countries is not analysed in terms of the growth in
interactions among countries, but in terms of the matrix distribution of relative frequencies of
interactions among countries. The degree of integration of a supranational system can then be
indicated in terms of interaction biases among participating countries as measured by the
difference between the observed distribution of interactions and the hypothetical distribution
of random interactions.2
In this study, the indicator of integration is applied to yearly data on collaborations among
European research institutions as listed in the Science Citation Index during the period 1993-
2000. Collaborations are counted by publications containing multiple institutional addresses,
and each co-occurrence of two institutional addresses counts as an interaction. In this way, a
matrix can be constructed of intra-national and international collaborations. The application of
the indicator provides one with a comprehensive measurement of integration of the European
science system and the development hereof over time. Other social and economic systems can
be analysed in the same way. We will elaborate on other applications in the final discussion
section.
2. International collaboration in science
International collaboration in research is expected to generate important benefits in many
ways. The rationales for collaboration can be divided in economic benefits and intellectual
benefits. Collaboration provides economic opportunities to realise economies of scale, for
example, with regard to costs of training and research infrastructures (Katz and Martin, 1997).
European examples of such large research infrastructures that have emerged through
intergovernmental collaboration, are the European Space Agency (ESA) and European Centre
for Nuclear Research (CERN). Collaboration is also expected to generate intellectual benefits
from the cross-fertilisation of ideas that previously were unconnected and from a better
quality control through internal refereeing. More generally, collaboration is intellectually
1 I thank Bas van Waveren and two referees for helpful comments. All errors are my own.
2 The indicator will be used here to analyse the integration process among countries into a
supranational system, but the indicator can equally be applied to lower levels (e.g., integration of cities
in a regional system, integration of regions in a national system). In this context, the indicator may be
of relevance in urban and regional studies.