  This paper challenges recent research (Evans, 2008) reporting that the
concentration of cited scientific literature increases with the online
availability of articles and journals. Using Thomson Reuters' Web of Science,
the present paper analyses changes in the concentration of citations received
(two- and five-year citation windows) by papers published between 1900 and
2005. Three measures of concentration are used: the percentage of papers that
received at least one citation (cited papers); the percentage of papers needed
to account for 20, 50 and 80 percent of the citations; and, the
Herfindahl-Hirschman index. These measures are used for four broad disciplines:
natural sciences and engineering, medical fields, social sciences, and the
humanities. All these measures converge and show that, contrary to what was
reported by Evans, the dispersion of citations is actually increasing.
