  The phenomenon of rankings is intimately related with the government interest
in fiscalizing the research outputs of universities. New forms of managerialism
have been introduced into the higher education system, leading to an increasing
interest from funding bodies in developing external evaluation tools to
allocate funds. Rankings rely heavily on bibliometric indicators. But
bibliometricians have been very critical with their use. Among other, they have
pointed out the over-simplistic view rankings represent when analyzing the
research output of universities, as they consider them as homogeneous ignoring
disciplinary differences. Although many university rankings now include league
tables by fields, reducing the complex framework of universities' research
activity to a single dimension leads to poor judgment and decision making. This
is partly because of the influence disciplinary specialization has on research
evaluation. This chapter analyzes from a methodological perspective how
rankings suppress disciplinary differences which are key factors to interpret
correctly these rankings.
