Every year, international surveys are published in the attempt to benchmark universities around the world against each other. The methodology in the rankings vary, but often include peer reviews, research articles published in important research magazines, number of Nobel Prizes won etc.
Sometimes, individual surveys adjust their metholody which can explain why the results can vary from year to year.
|University of Copenhagen's placement on rankings||World||Europe|
|QS World University Rankings (2012)||51||13|
|THE World University Rankings (2012)||130||50|
|Academic Ranking of World Universities - Shanghai (2012)||44||10|
|Leiden Ranking* (2013)||37||5|
|Leiden Ranking** (2013)||140||53|
* Based on total number of publications
** Based on "Mean Normalized Citatation Score"