APEX RATINGS: AN EXPLANATION
From "DIVIDING THE SPOILS", August 10, 2005

APEX (Annual Progeny Earnings Index) ratings are a series of indexes, which rate stallions in 17 different categories of progeny performance. The signature index, which is called the ‘A Runner Index', began life as an attempt to modify the impact of one huge earner (Spend A Buck, at the time, for his sire, Buckaroo, in 1985) on a sire's cumulative averageearnings index. It does this by measuring the frequency with which a sire's runners reach the top two percent of earners, each year. In North America, this is about $110,000, so any horse who earns that amount is designated an ‘A Runner'. The next two percent (about $75,000, at the moment) are called ‘B Runners,' and the next four percent (about $50,000) are ‘C Runners.' Those three groups combined--the top eight percent--are called ‘ABC Runners.'

If the top two percent of all earners are designated as ‘A Runners,' then a sire's A Runner Index is calculated by whether he has +/- two percent ‘A Runners' from Runners in a year, and by how much. For A and B Runners, two percent equals an Index of 1.00, which is average. The higher the better: six percent A Runners equals a 3.00 A Runner Index. For C Runners, four percent equals 1.00, and when you combine A+B+C Runners, eight percent equals 1.00.

This method also enables us to combine or compare ratings in different regions, namely: North America (U.S. plus Canada); ‘Europe' (Great Britain & Ireland, which are combined; France; and Germany); and Japan. Different thresholds for each category are established in each jurisdiction, and are then totaled up to give the overall picture. World Number Two A.P. Indy, for example, has a 5.31 A Runner Index in North America (astronomical), and 2.41 in Japan, but only 0.76 in Europe; so, combined, his A Runner Index is 4.76. Of the 17 ratings (indices) for each sire, 12 are these regional and overall class gradations: A, B, and C Indexes in North America, Europe, Japan, and Overall. Then there is the Overall ABC Index, and four ‘ABC Age Indices,' which tell us a stallion's proficiency at siring ABC Runners as two-year-olds; three- year-olds; four-year-olds; and five-year-olds and up. While the Overall A Runner Index is the most important rating, these other ratings often shed a very interesting light on what particular sires are really best at.

Finally, two other limitations: the indices are all calculated on what is called a ‘rolling' seven-year timescale, meaning only the last seven years are used for these calculations (that puts once-great sires in a more current perspective); and only sires who had ten or more three-year-old foals of the last year covered are eligible for rating. That eliminates the bottom, and results in a scale where 1.00 really does equal average, whereas the cumulative average-earnings index tends to make sires look better than they really are, at least in the commercial sire world.