Average earnings index (AEI) is a popular statistic used in North American Thoroughbred horse breeding.
It is used to put the earnings of a breeding animal's progeny into proper perspective.
It was only with the addition of computer power beginning in the 1970s and 1980s that a full analysis of mares could be added to the equations and determine the AEI for various crosses.
The AEI figures for various leading American sires are: As noted above, a stallion's career AEI can be found by looking up the pedigree of any of their offspring in The Jockey Club's online pedigree database, equineline.com.
However Racing Post warns details of horses trained outside GB and Ireland may be incomplete.