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AEI/CI Explained

AEI (Average Earnings Index)was developed by the late Joe Estes former editor of The Blood Horse. He wanted to develop a statistical method of appraising the performance at stud of both sires and mares based on the earnings of their progeny annually. Utilizing a numerical index where 1.00 represents the average for the breed, AEI reveals the earnings for any horse relative to his or her peers during the same year. For example, if the average earnings for a 3 year old horse during a specific season was $10,000, and your 3 year old had earned $15,000 during the same season, its AEI would be 1.50.

The CI (Comparative Index) tries to give us an idea of the quality of foals out of the same mares, but sired by different stallions. The aim is to determine whether or not a stallion is improving on his opportunities ( "upgrading his mares") or downgrading mares bred to him. The CI is derived by taking the average AEI of a mares foals sired by different sires. For example, in a hypothetical scenario where a sire was bred to just one mare, and the AEI's for her previous foals were 2.00, 1.50, and 1.00, the sire's CI would be 1.50, the average for the mare's other foals

The majority of sires at stud fail to upgrade their mares during their stud career. In modern times the most successful sire in Australasia has been Danehill whose lifetime AEI / CI figures reveal that he was able to upgrade mares mares bred to him by 51%. It comes as somewhat as a surprise to discover that many stallions considered to be successful in fact downgrade their mares. Many sires are reliant upon the quality of mare bred to them to maintain their lofty reputations.

Below is a list of stallions who have stood in the Northern Hemisphere that are represented in Australasia. AEI / CI figures are freely available for their Northern Hemisphere progeny which allows local breeders an opportunity to assess their performance in those regions. These figures have proven to be a reasonably accurate predictor of the subsequent performance of these sires at stud in Australasia. AEI / CI figures are available for GONE FOR REAL and have been included in the table in an effort to underline the potential which he offers to New Zealand breeders.

Northern Hemisphere Sires AEI / CI

Sire AEI CI Up/Dwn %
Danehill 3.09 2.04 51%
Gone For Real 1.39 0.96 45%
Dehere 1.90 1.60 19%
More Than Ready 2.16 1.95 11%
Helmsman 1.17 1.11 5%
Cape Cross 1.64 1.69 -3%
Van Nistelrooy 1.48 1.52 -3%
Stravinsky 1.74 1.84 -5%
Royal Academy 1.65 1.75 -6%
Tale of The Cat 1.71 1.92 -11%
Elusive Quality 2.04 2.43 -16%
Red Ransom 1.75 2.16 -19%
Anabaa 1.75 2.32 -24%
Storm Creek 1.03 1.56 -34%
Fusaichi Pegasus 1.75 2.70 -35%