  Empirical evidence demonstrates that citations received by scholarly
publications follow a pattern of preferential attachment, resulting in a
power-law distribution. Such asymmetry has sparked significant debate regarding
the use of citations for research evaluation. However, a consensus has yet to
be established concerning the historical trends in citation concentration. Are
citations becoming more concentrated in a small number of articles? Or have
recent geopolitical and technical changes in science led to more decentralized
distributions? This ongoing debate stems from a lack of technical clarity in
measuring inequality. Given the variations in citation practices across
disciplines and over time, it is crucial to account for multiple factors that
can influence the findings. This article explores how reference-based and
citation-based approaches, uncited articles, citation inflation, the expansion
of bibliometric databases, disciplinary differences, and self-citations affect
the evolution of citation concentration. Our results indicate a decreasing
trend in citation concentration, primarily driven by a decline in uncited
articles, which, in turn, can be attributed to the growing significance of Asia
and Europe. On the whole, our findings clarify current debates on citation
concentration and show that, contrary to a widely-held belief, citations are
increasingly scattered.
