I am not sure how realible these are. But they come from the data collected from around 18000 students from their respective schools. Harvard and Warton ae not in the list, because they do not paricipate in such surveys.
In europe, the firms give importance to FT rankings, forbes and the EIU. These are only 2 rankings that they follow. I do not see IESE taking long time to climb the spots in FT rankings as well. The placements this were just awesum, with an average salary shooting up like 148K (US$).
Giving another SHOT