Awards
The participants are ranked based on their individual scores. Medals are awarded to the highest ranked participants, such that slightly less than half of them receive a medal. Subsequently the cutoffs (minimum scores required to receive a gold, silver or bronze medal respectively) are chosen such that the ratio of gold to silver to bronze medals awarded approximates 1:2:3. Participants who do not win a medal but who score seven points on at least one problem receive an honorable mention.
Special prizes may be awarded for solutions of outstanding elegance or involving good generalisations of a problem. This last happened in 2005 (Iurie Boreico), 1995 (Nikolay Nikolov, Bulgaria), and 1988 (Emanouil Atanassov, Bulgaria), but was more frequent up to the early 1980s. The special prize in 2005 was awarded to Iurie Boreico, a student from Moldova, who came up with a brilliant solution to question 3, which was an inequality involving three variables. Boreico was one of only three students to achieve a perfect score for that paper.
The rule that at most half the contestants win a medal is sometimes broken if adhering to it causes the number of medals to deviate too much from half the number of contestants. This last happened in 2010, when the choice was to give either 226 (43.71%) or 266 (51.45%) of the 517 (excluding the 6 from North Korea — see below) contestants a medal, and 2012, when the choice was to give either 226 (46.35%) or 277 (50.55%) of the 548 contestants a medal.
Read more about this topic: International Mathematical Olympiad