From the Italian site ROARS: Return on Academic Research (Google translation):
According to the ranking Quacquarelli Symonds (QS) in Siena that something would happen in a year they have lost 220 (two hundred) rankings. But Pavia and Turin have collapsed by over 150 people coming out of the top-500; They have lost more than 100 positions Pisa, Tor Vergata, Federico II of Naples, Milan Catholic, Genoa, Perugia and Bicocca. The meltdown is simply due to the fact that QS has changed the methodology used in its construction ranking. Gaining places only the Polytechnics of Milan and Turin, as provided by Richard Holmes more than a month ago, when the news was spread of the change in methodology. I hope that the collapse of the Italian university in 2015 "certified" by QS and caused by the change of methodology, be a lesson: the rankings are not a serious way to evaluate the performance of universities.Unfortunately, judging from press and of POLIMI POLITO, it seems that the lesson has been helpful.