Page 280 - Becoming Metric Wise

272 Becoming Metric-Wise

This indicator shows if the research group is conservative in its
publication attitude, in the sense of publishing in journals with a
rather low impact (JCSm/FCSm , 1), or more daring (JCSm/
FCSm . 1) in its submission policy.

8.5.2 The Ratio of Averages Versus the Average of Ratios
Problem

A few years ago colleagues such as Lundberg (2007) and Opthof &
Leydesdorff (2010) criticized the (meanwhile corrected) “Crown indica-
tor” of CWTS stating that ratios of averages only make sense when applied
on data that are normally distributed. A better approach would be to con-
sider the average of the ratio of observed data (say number of received cita-
tions) and an expected value (such as the average number of citations in
the field). However, this approach does not completely solve the problem
as one must still define ‘the field’ and the proper citation window.
Ratios of averages and averages of ratios, in the context of impact fac-
tors, have been introduced by Egghe and Rousseau (1996a,b), see
Subsection 6.7.3. Clearly, the average impact factor is an average of ratios
(AoR), while the global impact factor is a RoA. In the context of
research evaluation an AoR is the better approach. Yet, we claim that the
impact of a field can best be described as an RoA. We recall that when
geometric means are used instead of arithmetic ones, the AoR verus
RoA problem disappears.

8.6 TOP X% PUBLICATIONS

According to CWTS the proportion of top 10% cited publications (also
known as the T indicator) is the best, i.e., most robust and size-
independent, indicator for the quality of an institute’s publications. By the
term “top 10% publications” CWTS means the top 10% most frequently
cited among similar publications, i.e., published in the same field, the
same publication year and being of article or review type (in the WoS).
Dividing by 10 yields that 1.0 is the expected global norm and one can
compare an institute’s (or research group’s) performance with this global
norm. Concretely if 12% of an institute’s publications belong to the top
10% of its field, then this institute is performing rather well, while if 6%
of an institute’s publications belong to the top 10% of their field, then
this institute is performing rather poorly. Similarly one may consider top
5% or top 1% publications.