  Pressured by globalization and the increasing demand for public organisations
to be accountable, efficient and transparent, university rankings have become
an important tool for assessing the quality of higher education institutions.
It is therefore important to carefully assess exactly what these rankings
measure. In this paper, the three major global university rankings, The
Academic Ranking of World Universities, The Times Higher Education and the
Quacquarelli Symonds World University Rankings, are studied. After a
description of the ranking methodologies, it is shown that university rankings
are stable over time but that there is variation between the three rankings.
Furthermore, using Principal Component Analysis and Exploratory Factor
Analysis, we show that the variables used to construct the rankings primarily
measure two underlying factors: a universities reputation and its research
performance. By correlating these factors and plotting regional aggregates of
universities on the two factors, differences between the rankings are made
visible. Last, we elaborate how the results from these analysis can be viewed
in light of often voiced critiques of the ranking process. This indicates that
the variables used by the rankings might not capture the concepts they claim to
measure. Doing so the study provides evidence of the ambiguous nature of
university ranking's quantification of university performance.
