Citation impacts revisited: How novel impact measures reflect interdisciplinarity and structural change at the local and global level
Résumé
Citation networks have fed numerous works in scientific evaluation, science mapping (and more
recently large-scale network studies) for decades. The variety of citation behavior across scientific
fields is both a research topic in sociology of science, and a problem in scientific evaluation.
Normalization, tantamount to a particular weighting of links in the citation network, is necessary
for allowing across-field comparisons of citation scores and interdisciplinary studies. In addition
to classical normalization which drastically reduces all variability factors altogether, two tracks of
research have emerged in the recent years. One is the revival of iterative “influence measures”. The
second is the “citing-side” normalization, whose only purpose is to control for the main factor of
variability, the inequality in citing propensity, letting other aspects play: knowledge export/
imports and growth. When all variables are defined at the same field-level, two propositions are
established: (a) the gross impact measure identifies with the product of relative growth rate, gross
balance of citation exchanges, and relative number of references (b) the normalized impact identifies
with the product of relative growth rate and normalized balance. At the science level, the
variance of growth rate over domains is a proxy for change in the system, and the variance of
balance a measure of inter-disciplinary dependences. This opens a new perspective, where the
resulting variance of normalized impact, and a related measure, the sum of these variances
proposed as a Change-Exchange Indicator, summarize important aspects of science structure and
dynamism. Results based on a decade’s data are discussed. The behavior of normalized impact
according to scale changes is also briefly discussed. A shift towards a network-based definition of
domains, more in the nomenclature-free spirit of citing-side normalization than database classification
schemes, appears promising, albeit with technical challenges. An appealing issue is the
connection with macro-level life-cycles of domains, and the dynamics of citation network.
Mots clés
analyse des citations
réseau de citation
normalisation de citation
normalisation côté citant
citation fractionnée
opération de citation
système scientifique
évolution scientifique
citation analysis
citation network
citation normalisation
citing-side normalisation
source-level normalisation
a priori normalisation
fractional citation
citation transactions
scientific system
scientific change
interdisciplinarity