[1] It was an assessment of Thoroughbred racehorses issued by the International Federation of Horseracing Authorities (IFHA) in January 2009.
[2] It included horses aged three or older which competed in flat races anywhere in the world during 2008.
It was the first edition to be open to all horses irrespective of where they raced or were trained.
This year's joint-highest ratings were awarded to Curlin for his performances in both the Dubai World Cup and the Stephen Foster Handicap, and to New Approach for his win in the Champion Stakes.
It also shows the leading performers in various subdivisions of each group, which are defined by the distances of races, and the surfaces on which they are run.