Explanation of Performance and Production Indexes
When you read through the Stakes Winners section of The
Blood-Horse and the Stakes Results section of Thoroughbred
Times, you will notice the performance summaries of stallions
contain production indexes such as SI, AEI, CI, ComSI, etc. Below,
these indexes and other performance and production indexes found in
the above-mentioned publications as well as other publications are
defined.
Racing Index (RI)
The RI is based on the average earnings per start of runners in
North America. The RI is calculated by taking all foals born in a
given year and determining that crop's average earnings per start
for each year that it raced. Colts and fillies are separated for the
calculation. After five years of racing, a runner's RI does not
change, even if it continues to race. The average earnings per start
for a crop for a given year is set at 1.00. A RI of 2.00 would have
earned twice as much per start during a given year as a horse of the
same sex, from the same crop with a RI of 1.00
Sire Index (SI)
An average of the RIs for all of the stallion's foals that have
started three or more times in North America.
Comparable Sire Index (ComSI)
The average of the RIs of progeny produced from mares bred to
subject stallion, excluding foals by subject stallion.
Average Earnings Index (AEI)
An index of the lifetime earnings of a sire's runners compared to
the average of all runners in the same years; average earnings of
all runners in a given year is set at 1.00.
Comparable Index (CI)
The average earnings of progeny produced by mares bred to one
stallion when they were bred to other stallions.
Broodmare Sire Index (BSI)
An average of the RI of all foals out of the sire's daughters that
started at least three times. For BSI to be calculated, a broodmare
sire must be represented by a minimum of 75 starters lifetime.
