  When scientometric indicators are used to compare research units active in
different scientific fields, there often is a need to make corrections for
differences between fields, for instance differences in publication,
collaboration, and citation practices. Field-normalized indicators aim to make
such corrections. The design of these indicators is a significant challenge. We
discuss the main issues in the design of field-normalized indicators, and we
present an overview of different approaches that have been developed for
dealing with the problem of field normalization. We also discuss how
field-normalized indicators can be evaluated, and we consider the sensitivity
of scientometric analyses to the choice of a field normalization approach.
