An impact value (IV) is an index figure calculated by dividing the percentage of winners possessing a particular characteristic (for example, sporting first-time headgear) into the percentage of runners that possess the characteristic.
A value of 1.00 would indicate horses with a particular characteristic win no fewer or no more than those without that characteristic. Below 1.00 is indicative of underperformance, above 1.00 is above expectation.
In this release, the IV calculations have been altered in that they are now calculated on a line by line basis as follows
- (runs divided by wins) divided by (no of races divided by no of runners in races)
This means an IV can be calculated for any individual line rather than comparing a group of items against each other. Therefore you can now compare individual items such as a trainer’s record with headgear.
Also the place IV and win and place IV also now recalculated in the same way.