Framing a market, scratchings

We’ve already had a look at framing a market. There’s quite a bit to it but once you have your head around the maths of it, it’ll all be very simple. But once you’re done, how do you deal with a spanner in the works? When it comes to rating a race, that spanner comes in the form of scratchings.

When a horse is taken out, it shifts the complexion of the race.. and more importantly, the market.

The effect of scratchings

The key basic to remember is that a scratching improves the hopes of every other horse – they now have one less opponent to beat.

In theory, all you have to do is remove the scratched horse from your numbers and restate the chances of every other runner.

Scratchings: the market

Let’s look at the example from our ‘Framing a market’ guide:

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For a simple example of a scratching, let’s say Horse B is taken out of the race.

After the market is adjusted it looks like this:

The market is still constructed the same way, it’s simply done so without the scratched horse. The probability factor for each horse is the same. But the total is obviously lower, so the market percentages move in line.

That’s how the scratched horse’s percentage is re-distributed across the remaining field.

Scratchings: what information do you need?

It’s fine to do all of this if you’ve set the market yourself. But what if you’re following somebody else’s prices? Can you still reset the market for a late scratching?

Yes – all you need is the rated prices.

Rated prices can quite easily be converted to the market percentage, from which you can reset after a scratching.

Again, let’s check at an example…

It’s just a case of taking the market percentage of the remaining runners, and restating them to 100% by redistributing the scratched horse’s percentage to each horse in line with their chances. Simple, right?

If it doesn’t feel simple now, it will once you have your head around it.

Having a model which can quickly readjust things for you in the event of a scratching is very, very useful: especially when they happen behind the barriers and you only have minutes, or even seconds, to recalibrate your bets. A great example of this is the Melbourne racing ratings sheet with Trevor Lawson’s Melbourne Ratings service. The Excel-based ratings sheet has a simple function where you just tag a horse as “Scratched”, and the race restates everything – new rated prices and recommended stakes – with the click of that button. Check out Melbourne Ratings here.

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