Impact Value – Hedger Pro

Introduction

Impact Value (IV) shows how strongly a horse’s price came in during the race, compared with what is normal for a horse at that starting price.

Score	Meaning
0	The price never went below the Betfair starting price (BSP).
50	The price came in to about the typical in-play low for that BSP.
100	The price traded at 1.01.

Higher means more in-play market support. 50 is not an average horse. It means about what we usually see for a horse at this price.

Why compare with a typical move?

Winners usually trade at or near 1.01 at some point in-running, and well-fancied horses often trade much shorter than their BSP even when they lose. So simply asking whether the price shortened is not very informative: most fancied runners do.

Impact Value instead asks whether the price came in more or less than is normal for a horse at that price. That makes a 2.0 favourite and a 20.0 outsider comparable on the same scale.

How it is calculated

The typical in-play low

From a large set of historical races, we have fitted a curve that predicts the typical in-play low for any BSP.

For example, a horse with a BSP of 5.0 (a 20% chance) typically trades down to about 2.15 at some point during the race.

The score

The horse’s actual in-play low, the shortest price matched on Betfair during the race, is placed on a scale with three fixed points:

In-play low	Score
Equal to the BSP (no shortening)	0
Equal to the typical low for that BSP	50
1.01	100

Between those points the score rises in a straight line. Because the typical low sits at 50, the scale is in two halves: from BSP down to the typical low (0-50), and from the typical low down to 1.01 (50-100).

Example: a horse starting at 5.0

In-play low	Score	Why
5.0	0	No shortening at all.
3.0	35	Came in, but less than is typical for a 5.0 shot.
2.15	50	Exactly the typical in-play low.
1.5	79	Came in well beyond the typical low.
1.01	100	Traded at the minimum price (usually a winner, or very close to one).

At very extreme prices, a simple straight line from BSP (0) to 1.01 (100) is used instead.

Single run and form

Per run

Each run gets one Impact Value. Use it to see whether a particular run attracted strong or weak in-play support.

Rolling form

On horse, jockey and trainer profiles, the rolling Impact Value is the average across all their runs in the period:

rolling IV = total of Impact Values / number of runs

This shows whether they tend to attract in-play money, not just what happened once. Best, worst and trend figures work as described in the statistics overview.

Normalised Impact Value

The normalised score is a 0-100 percentile against all rolling Impact Values for the same entity type and period, for example all horse 1-year figures. A normalised IV of 80 means the rolling IV is better than about 80% of them.

It is not another version of the per-run 0-100 score. See normalised scores.

How to use it

Use IV when you care about market behaviour in-running, not just the result or the starting price.
IV, PD and BR all measure in-play price moves. IV is the only one that adjusts for what is normal at each price. See In-play price moves for how they differ.
Pair it with BSP: a 10.0 shot that trades at 4.0 and a 2.0 favourite that trades at 1.8 can score very differently.
For jockeys and trainers, rolling figures bunch together because many runs average out, so the normalised score is usually more useful.
Winners usually trade at or near 1.01 and score close to 100, so a high IV goes hand in hand with winning often.