  The Center for Science and Technology Studies at Leiden University advocates
the use of specific normalizations for assessing research performance with
reference to a world average. The Journal Citation Score (JCS) and Field
Citation Score (FCS) are averaged for the research group or individual
researcher under study, and then these values are used as denominators of the
(mean) Citations per publication (CPP). Thus, this normalization is based on
dividing two averages. This procedure only generates a legitimate indicator in
the case of underlying normal distributions. Given the skewed distributions
under study, one should average the observed versus expected values which are
to be divided first for each publication. We show the effects of the Leiden
normalization for a recent evaluation where we happened to have access to the
underlying data.
