  Despite having an important role supporting assessment processes, criticism
towards evaluation systems and the categorizations used are frequent.
Considering the acceptance by the scientific community as an essential issue
for using rankings or categorizations in research evaluation, the aim of this
paper is testing the results of rankings of scholarly book publishers'
prestige, Scholarly Publishers Indicators (SPI hereafter). SPI is a public,
survey-based ranking of scholarly publishers' prestige (among other
indicators). The latest version of the ranking (2014) was based on an expert
consultation with a large number of respondents. In order to validate and
refine the results for Humanities' fields as proposed by the assessment
agencies, a Delphi technique was applied with a panel of randomly selected
experts over the initial rankings. The results show an equalizing effect of the
technique over the initial rankings as well as a high degree of concordance
between its theoretical aim (consensus among experts) and its empirical results
(summarized with Gini Index). The resulting categorization is understood as
more conclusive and susceptible of being accepted by those under evaluation.
