collaborations may fragment in a number of islands of collaborating countries. The question is
whether the increase in collaborations, as a general phenomenon, also contributed to a more
integrated pattern of collaborations.
The hypothesis holds that European science indeed evolved towards a more integrated
system. However, in an empirical research design, the hypothesis of increasing integration
requires further specification. What does it mean that a set of countries becomes more
integrated? Below, I address this hypothesis using data on both national and European
collaborations as indicated by publications with multiple addresses. European integration,
then, can then be analysed by comparing the propensities of countries to collaborate
nationally with the propensity to collaborate with other European member states. It is crucial
to distinguish intra-national from international collaboration, because, other things equal,
larger countries are expected to collaborate relatively more often nationally than
internationally, simply because there exist more potential national partners in larger countries
than in smaller countries. Controlling for differences in size of countries leads us to specify
two hypothesis:
1. European integration increases over time as indicated by a declining bias to
collaborate nationally controlling for differences in size of countries.
2. European integration increases over time as indicated by a convergence in the bias of
each pair of countries to collaborate controlling for differences in size of each of the
countries.
3. A new measure of integration
An inter-institutional collaboration is here defined as a pair of different institutional addresses
occurring in a publication record contained in the Science Citation Index. Note that this
definition is not restricted to co-authorship as one and the same person can be associated with
more than one institution. 3
The number of inter-institutional collaboration between two European member states i
(i=1,..,15) and j (j=1,..,15) as a share of the total number of collaborations is denoted as qij ,
which results in a 15x15 matrix of 225 qij-values. National collaborations are present on the
3 More on this, see Katz and Martin (1997: 11-13).