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/ Simon Rowlands / 07 March 2011 / Leave a Comment 
What will the going be described as on day one?
Our blogger takes a look at three of the Cheltenham Festival Specials markets available on Betfair...
With the Cheltenham Festival approaching fast, various specials markets have started springing up all over the betting industry. Some of these represent little more than 'hit and hope' jobs at this stage, but it is surprising to discover just how far a modest amount of research can take you with the others.
I decided to look at the markets for official going, winning distances and longest SP.
The following is the historical data since 2001, the year in which the meeting was cancelled due to foot and mouth:
The official going market is settled according to the official description of the majority of the ground on the hurdle course prior to the first race of the meeting. In this, it is subject to human interference in both the imperative to achieve a certain outcome ("good jumping ground") and in the possible inclination to believe that that outcome has been achieved, come what may (what might be termed the "mark your own exam paper" phenomenon).
Simon Claisse has been Clerk of The Course at Cheltenham since 2000 and Timeform, using race times as well as other information, has disagreed with his description in four of the last five years.
In other words, it matters little what the ground is, if Mr Claisse states it is "good", or more commonly "good to soft", that is what you will get paid out on. He even changed it from "good to soft" to a more credible "good" halfway through the first day of last year's meeting.
Claisse consults with famed weather forecaster John Kettley in the weeks leading up to the meeting and waters as he sees fit. Current odds of [1.42] on Betfair suggest that Claisse will achieve his goal of describing the ground for the first as "good to soft".
The state of the going - real, rather than imagined - has an impact on many other markets, not least that of winning distances. Wider modelling of margins confirms that they increase as the ground becomes softer, though more gradually than might be supposed.
Gauging the real significance of winning distances at the Cheltenham Festival has been akin to trying to herd cats over the years. Not only has the going varied, but the numbers and types of races have varied, too, as has the means by which the margins themselves are determined.
The meeting went from being a three-day one to a four-day one after the 2004 Festival, and there will be another race - making 27 in all - this year. That race is a two-and-a-half mile novice handicap chase, while the Jewson Chase becomes a non-handicap.
The final column in the spreadsheet takes into account the different means of returning winning margins prior to 2009 and adjusts those margins up to 27 races on a pro-rata basis. It is not that simple, of course, but it is some sort of a guide.
The average of this column is 102, which is close to the midpoint of both the winning distance odds market and the winning distance line market, but the median is just 92.
It seems to me as if a couple of wide-margin years recently (one of which was run on genuinely testing ground) might have skewed people's perception. There is also a tendency for people to bet "high" - to want something to happen, rather than not happen - with these markets.
A sell of the winning distance line at 100 or more and a back of winning distance odds of less than 90 lengths makes appeal unless there seems a good likelihood of conditions turning testing. It should be noted that any abandoned or voided races will be made up at 10 lengths (see rules tab), even though the average winning margin has been just under 4 lengths.
The longest SP winner market is divided into "shorter than 33/1", "longer than 50/1" and in between. Bear in mind that just one instance of a rank outsider will trump everything else, and that, in the absence of that, just one instance of an in-between winner will trump the shorter-priced category. 187 of 209 races (89.5%) have been won by "unders", 21 races (10%) by "in between" and just 1 race (0.5%) by "overs".
If you convert that into probabilities, the implication is that the true odds should, respectively, be something like: [15.0]; [1.23]; and [8.2]. In the last nine years, the in-between category has prevailed eight times and the rank outsiders once.
I am, however, very sceptical that this is representative. A better measure - one which shows the middle category to have been overperforming greatly (and probably randomly) against expectation - is likely to be the average amount of the book taken up by each category in races in which a horse's true chance has been established from the Betfair SP.
This eliminates the so-called favourite-longshot bias and produces expected figures of 93.5% unders, 5.5% in between and 1% overs. The resulting probabilities produce (by my reckoning) estimated likely odds of [1.84] in between; [4.2] overs; and [4.6] unders.
It may seem counter-intuitive, but, with the market as it is, unders looks the best bet. It could be expected to come off only about 22% of the time, and has done so not once recently, but [8.0] is too big if you believe theory and past market expectation rather than potentially misleading evidence.
Our blogger takes a look at three of the Cheltenham Festival Specials markets available on Betfair......
Timeform's Phil Turner joins Alan Dudman to discuss the Arkle, the Jewson and the RSA Chase....
Timeform's Harry Bowles joins Alan Dudman to run his eye over the four Grade 1 novice hurdles at the Festival....
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