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AE Index Value
A/E Index Value
Most racing researchers when sharing past statistics with their readers give the following breakdown: Wins, Bets, Strike Rate, Profit/loss, Return on Investment.
Now for most people this is the type of information they want – they want to see whether:
a) it was a decent sample size (indicated by the number of wins/bets);
b) what the chance the bet has of winning (indicated by the strike rate);
c) what chance they have of making money (indicated by the profit/loss figure);
d) how profitable or not the selections are in percentage terms (indicated by the return on investment figure).
However, there are problems with this type of information in terms of the fact that a couple of big priced winners can skew the overall figures. For example you may get say the following set of figures:
On the face of it – everything looks pretty rosy. A decent sample size, a decent strike rate and a solid looking profit. However, what if there had been two winners at say 40/1 and 33/1? Taking those out of the equation gives us this:
Suddenly the figures start to look less good – the ROI% has gone down nearly 50%!
What I often do when quoting raw figures, is check to see if there are any big priced winners that may have affected the overall figures. Indeed, I often split the original data up into price bands, which helps to show any such anomalies.
However there are other options – one such option is to look at something called the A/E index. The A/E index is a type of impact value. The A stands for ‘Actual’ and the E stands for ‘Expected’ so essentially the stat shows an index of actual winners to expected winners. To give you a numerical explanation – imagine you had a system that generated 10 selections from horses that were Even money. Each horse would have a 50% chance of winning according to the price and hence in 10 runs you would expect 5 winners (50%). Imagine that 7 of the horses won – so that gives us:
A = 7 winners
E = 5 winners
A/E index = 1.4 (7 divided by 5)
The higher the A/E index the better from a potential backing perspective; any figure over 1 gives us a potentially positive scenario.
The main advantage of looking at the A/E index is that it is useful for determining value selections as it takes into account the prices of all the runners. The slight downside is that it cannot take the bookie’s over round into account so giving us slightly ‘skewed’ results.
For the remainder of the article my focus is turf flat racing with the data is taken from 2007-2011. I wanted to now look at the A/E index in relation to favourites. The overall figure for all turf favourites during this period is 0.94. So fairly close to 1.00 and in general you don’t tend to lose huge amounts if you are a favourite backer. However, you do tend to lose in the long run. However, are any favourites better than others according to the A/E index? Let us have a look at some different favourite race types:
As we can see there is quite a difference in some of the favourite A/E indices. In general then it looks like there is more value to be had backing favourites in 2yo Group races, all selling races and all claiming races.
In terms of favourites at different courses again there are some differences worth noting:
Four of the courses with A/E figures below 0.90 are Grade 1 tracks. Whether these figures are skewed more thanks to bookmaker’s over round is difficult to say – it might simply be down to the more competitive nature of the racing at these tracks.
The A/E index is also useful for comparing trainers or jockeys etc. Here are some trainers with decent A/E indices from 2007-11.
Most of these trainers in this list are not that well known and hence from a value perspective runners from these stables are probably worth a second glance. Now a look at the trainers with the poorest A/E indices:
Personally I will be avoiding these trainers in the next few months.
Onto jockeys now – here are those with figures over 1.00:
It is quite heartening from a personal standpoint that several of the jockeys in this table are jockeys I like. I have been especially impressed with Julie Burke, Ahmed Ajtebi, Ryan
Clark and Harry Bentley. Now onto jockeys with less impressive figures:
It is quite heartening from a personal standpoint that several of the jockeys in this table are jockeys I like. I have been especially impressed with Julie Burke, Ahmed Ajtebi, Ryan Clark and Harry Bentley. Now onto jockeys with less impressive figures:
As with the ‘poor’ trainer table, these are jockeys I would not be rushing to put down my hard earned cash.
As we can see the A/E index can be used in a variety of ways looking at a variety of angles/data. Essentially the A/E index gives us another useful ‘weapon’ in our statistical armoury. Although I have essentially used it as a stand-alone figure in this article, I believe it is something we can best use in conjunction with strike rate and return on investment figures. Combining these should aid us considerably in our battle against the bookies.
Finally I must convey my thanks to www.flatstats.co.uk whose A/E indices I used for this article.
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