Monday, Jul. 21, 2014

How to Compile a Tissue in Horse Racing - Introduction

Articles TutorialsThere are several articles about how to compile a tissue floating about the internet. Almost all of them explain in great detail how to convert odds into the percentage chance they represent but, frustratingly, there seem to be very few (if any) that explain how to convert the findings of form analysis into the relative chance of a horse in a given race. If you can’t do this, it’s impossible to make a tissue.

For those that don’t know, odds can be expressed as a percentage by dividing the top number by the bottom, adding 1 then dividing the result by 100. A 7/2 shot, for example, is calculated as follows:

7/2 =3.5

3.5 + 1 = 4.5

100/4.5 = 22.22%

If the odds on offer are perfectly fair, the percentage chance of each horse will add up to 100. Bookmakers make profits by ensuring the odds on offer for a given event always add up to more than 100%.

Any casual observer of horse racing will be aware of at least some of the factors that influence a horse’s chance in a given race, with going, trip and recent form among the most widely accepted. In essence, the key to accurate odds-compilation is knowing how much weight to attach to each factor. For some horses, a particular factor might be irrelevant, for others it will be crucial. It’s not an exact science and there are occasions, such as with unraced horses, when an educated guess is the only option. This article is designed as an introduction to compiling tissues and will provide only the basics. However, I will flesh out some of the more complex aspects with additional pieces in due course. It will be apparent that I have a marked preference for National Hunt racing, but the fundamental principals also apply to that Flat. 

Several analysts claim the going is the most important factor but I disagree. I think it’s more logical to start off by assessing each horse’s ability, and the easiest way to do this is by using form ratings. Ratings won’t tell you everything, but I find them very useful in helping to build a framework for a tissue. Personally, I tend to compare official BHA ratings with Racing Post Ratings (RPR) then use my own judgment to gauge which is the more accurate. However, there are other options, such as Timeform or self-compiled ratings.

The first question I ask my self is; “What sort of rating is this horse capable of achieving?” For horses that have plenty of recent form, this should be fairly easy. For obvious reasons, it’s harder to gauge horses that are returning from absences, have appeared only sporadically in recent seasons or who seem badly out of sorts. At least some degree of guesswork has to be used in these situations, but it’s usually correct to assume that, to some extent at least, these horses will have regressed and it’s important not to place too much emphasis on form that is more than about 18 months old.

Once a rating for each horse has been established, it is necessary to adjust them to take into account the weights carried in the race in question. I usually adjust the weights to 12st, so a horse set to carry 11st 2lbs should have 12lb added to his rating. Once each rating has been adjusted, we have a framework in place on which we can make a tissue.

The next question to address is; “How likely is each horse to run to form”. There is an almost limitless number of factors that could be considered as part of this process but the main things to think about are:

- Current form

- Suitability of going

- Is the horse consistent?

- Is the race going to be run to suit the horse?

- Suitability of trip

- Horse’s form at the course and/or at courses with similar configurations

 If Flat racing is your bag, you may also need to make adjustments to take into account the draw.

The principle is to adjust the rating we have for each runner, either upwards or downwards, depending on the horse’s profile. Gauging the extent to which each rating should be adjusted is a very subjective process but it becomes easier with experience and in subsequent articles I will set out some guidelines. In addition, I will discuss the extent to which other factors such as trainer form, jockey booking and breeding should be assessed, and pick a race to use as a working example.

When the final ratings have been reached, I use the below “Lbs off Top Rated” scale to convert the ratings into odds:

0       1.00

1       0.90

2       0.80

3       0.67

4       0.57

5       0.50

6       0.40

7       0.33

8       0.25

9       0.20

10      0.14

11      0.11

12      0.08

13      0.06

14      0.05

15      0.04

16      0.03

17      0.03

18      0.02

19      0.01

20+     0.01

The horse with the highest rating is allotted a figure of 1.00, then each other horse is allotted the figure that corre sponds to the number of lbs below the top-rated horse its rating is.

The price for each horse is calculated by dividing the corresponding “Lbs off Top Rated” figure by the sum of the “Lbs off Top Rated” ratings for the entire field.

For example, the prices for a five-runner field with ratings of 136 (1.0), 134 (0.8), 133 (0.67), 129 (0.33) and 125 (0.11) is as below:

136     1.00/2.91 = odds of 2.91 (1.91/1)       

134     0.80/2.91 = odds of 3.64 (2.64/1)

133     0.67/2.91 = odds of 4.34 (3.34/1)

129     0.33/2.91 = odds of 8.82 (7.82/1)

125     0.11/2.91 = odds of 26.50 (25.5-1)