<p>In the knowledge economy, the measurement of the performance of universities makes it possible to follow the evolution and verify the effects of the management and also to compare universities and university systems with comparable measures provided through international university rankings. Using one of the most well-known and used rankings (ARWU), this paper checks the sensitivity and elasticity of his indicators, both with reference to universities and national university systems. We check the level of dependence on the ranking indicators, distinguishing indicators of an individual or institutional nature. Thus, the universities in the first third of ARWU and countries such as the USA, UK, Germany, and, especially, Japan or France are more dependent on individual indicators, such as Award-Alumni, than the rest of the countries. Besides that, these countries would lose positions if these indicators are not considered. The opposite would happen for the indicator number of publications. In addition, a clustering of the 1000 ARWU universities is made, obtaining a positioning of the universities (therefore of the university systems) in five clusters based on their sensitivity and elasticity to the ranking indicators. All this allows for identifying the strengths and weaknesses of universities and university systems in a knowledge economy, also used as benchmarking for decision-making in university management.</p>