Abstract :
In this article we distinguish between top-performance
and lower-performance groups in the analysis of statistical
properties of bibliometric characteristics of two large
sets of research groups. We find intriguing differences
between top-performance and lower-performance groups,
and between the two sets of research groups. These latter
differences may indicate the influence of research
management strategies. We report the following two
main observations: First, lower-performance groups
have a larger size-dependent cumulative advantage for
receiving citations than top-performance groups. Second,
regardless of performance, larger groups have
fewer not-cited publications. Particularly for the lowerperformance
groups, the fraction of not-cited publications
decreases considerably with size. We introduce a
simple model in which processes at the microlevel lead
to the observed phenomena at the macrolevel. Next, we
fit our findings into the novel concept of hierarchically
layered networks. In this concept, which provides the
“infrastructure” for the model, a network of research
groups constitutes a layer of one hierarchical step
higher than the basic network of publications connected
by citations. The cumulative size advantage of citations
received by a group resembles preferential attachment
in the basic network in which highly connected nodes
(publications) increase their connectivity faster than
less connected nodes. But in our study it is size that
causes an advantage. In general, the larger a group
(node in the research group network), the more incoming
links this group acquires in a nonlinear, cumulative
way. Nevertheless, top-performance groups are about an
order of magnitude more efficient in creating linkages
(i.e., receiving citations) than lower-performance groups.
This implies that together with the size-dependent mechanism,
preferential attachment, a quite common characteristic
of complex networks, also works. Finally, in the
framework of this study on performance-related differences
of bibliometric properties of research groups, wealso find that top-performance groups are, on average,
more successful in the entire range of journal impact.
