About APEX Ratings

APEX (Annual Progeny Earnings indeX) sire ratings were originally devised for the newsletter Racing Update in the late 1980’s as a variation on the average-earnings index. That calculation was itself an improvement on the standard Progeny Earnings tables, in that the average-earnings index at least divided a sire’s total progeny earnings in a year by his total number of runners, and compared a specific sire’s average earnings per runner with the average earnings for all runners by all sires. To cross jurisdictions (UK/Ireland, for example, or France), the calculation was done for each jurisdiction and the results added together.

There were two weaknesses with the average-earnings index which we addressed with APEX. The first was that one huge earner could skew the index beyond credibility. We addressed this by measuring the frequency with which a sire produced earners in three earnings categories: the top 2% of earners were designated ‘A Runners’; the next 2% ‘B Runners’; and the next 4% ‘C Runners’; we then also combined the three categories to create ‘ABC Runners’, which are the top 8% of earners.

The second weakness with the average-earnings index (and the cumulative average-earnings index, done over a sire’s career) is that, though the calculation is mathematically pure, taking all runners by all sires inflates the ratings for sires which matter to those operating in the thoroughbred marketplace, or what we have come to call the ‘commercial market’. A third of sires, and a fifth of foals, have no relevance to the practical world in which the vast majority of owners and breeders are operating. APEX is therefore less pure, but more practical, by virtue of two limitations on the population we study: we limit the analysis to the last seven years (which exposes once-great sires who have tailed off), and we require that sires have at least 10 named 3-year-olds in the last season covered (in this case, 2019, so 10+ foals of 2016). By making these two adjustments we have found that a 1.00 index really does mean an average sire, not 1.40 as we sometimes find with the average-earnings index.