  World University rankings have become well-established tools that students,
university managers and policy makers read and use. Each ranking claims to have
a unique methodology capable of measuring the 'quality' of universities. The
purpose of this paper is to analyze to which extent these different rankings
measure the same phenomenon and what it is that they are measuring. For this,
we selected a total of seven world-university rankings and performed a
principal component analysis. After ensuring that despite their methodological
differences, they all come together to a single component, we hypothesized that
bibliometric indicators could explain what is being measured. Our analyses show
that ranking scores from whichever of the seven league tables under study can
be explained by the number of publications and citations received by the
institution. We conclude by discussing policy implications and opportunities on
how a nuanced and responsible use of rankings can help decision making at the
institutional level
