  Questions of definition and measurement continue to constrain a consensus on
the measurement of interdisciplinarity. Using Rao-Stirling (RS) Diversity
produces sometimes anomalous results. We argue that these unexpected outcomes
can be related to the use of "dual-concept diversity" which combines "variety"
and "balance" in the definitions (ex ante). We propose to modify RS Diversity
into a new indicator (DIV) which operationalizes variety, balance, and
disparity independently and then combines them ex post. "Balance" can be
measured using the Gini coefficient. We apply DIV to the aggregated citation
patterns of 11,487 journals covered by the Journal Citation Reports 2016 of the
Science Citation Index and the Social Sciences Citation Index as an empirical
domain and, in more detail, to the citation patterns of 85 journals assigned to
the Web-of-Science category "information science & library science" in both the
cited and citing directions. We compare the results of the indicators and show
that DIV provides improved results in terms of distinguishing between
interdisciplinary knowledge integration (citing) versus knowledge diffusion
(cited). The new diversity indicator and RS diversity measure different
features. A routine for the measurement of the various operationalizations of
diversity (in any data matrix) is made available online.
