PIV is better than Impact Value

In my last post I talked about how you can use impact value to analyse the strength of pretty much any factor, rating or selections in any sport. Today I want to share with you an even more powerful way of doing this.

It is called Pool Impact Value or A/E. I personally prefer Pool Impact Value, a term made up (I believe) by US handicapper Dave Schwartz. In the UK it is more commonly referred to as A/E which stands as Actual / Expected.

PIV or Pool Impact Value makes much more sense to me and so is the terminology that I choose to use!

Calculating the pool impact value is done in a very similar way to calculating the impact value except this time we also include the pool, or in the UK the final or SP odds.

This creates a far more accurate figure because we know that usually the odds are a very accurate representation of a horses chance of winning.

So how are we going to calculate this figure?

You will be pleased to hear that it is much easier than you may expect. We are looking to calculate…

Winners / Expected Winners

The key is in how we calculate the expected winners and when calculating the PIV we used the odds to guide us.

To calculate the expected winners using the odds we use the simple sum…

1 / decimal odds

Decimal odds are the kind of odds you see on Betfair. They are figures such as 2.50 or 3.75 etc… Odds such as 3/1 and 5/1 are called fractional odds and you don’t want to use these with this method.

So if we have odds of 3.75 then we would do…

1 / 3.75 = 0.27

This actually gives us the probability that the horse is going to win the race based on the odds. A probability is the same as a percentage but divided by 100. So 0.26 is the same as 26%. In other words, the odds are telling us that this horse has a 26% chance of winning. We know that final odds are a very accurate estimate of a horses chance of winning and so we use this to calculate our expected winners.

In the sample of runners that we have taken from a particular tipster or rating we perform the sum…

1 / decimal odds

…for each of them. Then we add all of these decimal figures together and the final number will provide us with an accurate assessment of the expected winners based on the odds.

To create the PIV we simply now…

Winners / Expected Winners

…take the winners in our sample and divide it by the expected winners that we have just calculated. The final figure is your PIV or Pool Impact Value.

This works in the same way as the impact value in that anything higher than 1 means the horses are winning more than average and anything lower than one means that they are winning less than average.

The difference is that this is a much more accurate and powerful technique to use than impact value. Now you can go away and calculate whether your favourite selections are winning more or less than the average!

Tags: calculate, Impact Value, odds, PIV