Where the Model Disagrees With the Market at the St Leger

The model's top-rated runner at Doncaster this week is, in most of the races, not the horse the market has made favourite. The two also disagree about how likely the whole thing is. The model's figure for its own first choice sits below the market's figure for its favourite in almost every race we publish.

The record is clear about what that is worth. Across 9,568 races the market's prices have been the sharper forecast, a Brier score of 0.091 against the model's 0.100, on a measure that scores a stated probability against what actually happened and where the lower number is the better one. Backing the model's top pick flat at starting price across all of those races returns −14.0%. Where the two part company, the market has usually been the one closer to the result.

So the disagreement is worth reading. It is not a shortlist. A betting market is a large number of people with money at stake, and money concentrates. Our model sees ratings and form figures, and it has no access to the things the money knows, so it spreads the chance more evenly across a field than the market does.

That is why its first choice is so often a horse at a longer price, and why that fact on its own means very little. A flatter forecast will name more outsiders than a sharper one whether or not it has found anything.

What follows is the model's card for each day of the festival as it publishes, with the market alongside it, and a note on what the gap does and does not tell you.

Thursday: the May Hill Stakes

The Group 2 May Hill is the two-year-old fillies' championship of the meeting and the feature of the opening day.

Read it as two columns rather than a ranking. Model chance is what our model makes of each filly. Market is the chance implied by the starting price with the bookmaker's charge taken back out, so that column sums to a hundred and the two are comparable. The vs Market column states the difference in percentage points and nothing more, which is deliberate: a gap is a disagreement, not a valuation.

The table is sorted by the model's number, so the top row is the model's first choice. Look across that row to the Market column and the pattern from the opening section usually shows up on its own. The model's leading filly is rated lower by the model than the favourite is rated by the market, even when they are the same horse.

The wide gaps are worth a moment because of where they land. They tend to fall on horses in the middle and at the back of the market, the ones with the least money and the least attention on them, and those are exactly the runners a form-only model has the least information about. A large disagreement is generally a sign that the model is short of evidence rather than long on insight.

Friday's Doncaster Cup card, Saturday's Classic and Sunday's closing card are added here as each morning's estimates publish at 09:00 BST.

What we will say on Sunday, and what we will not

At the end of the meeting we will be able to count how often the model's first choice won and how often the market's favourite did. We will publish both, including the case where ours came out ahead, and it will still not mean the model has found an edge at Doncaster. Four days is a few dozen races. The all-time record runs to 9,568 of them and settles at −14.0%, and a good week inside a losing record is the most ordinary thing in betting.

That is why nothing here is presented as a selection. Our St Leger Festival tips page carries the form angles, the going and the draw for each of the four days, written as research. This page carries the model's arithmetic. Neither is a tip, and the model card does not become one because it puts a number beside a horse's name.

If the Market column is the part you want to understand, what chance is that price really giving my horse shows how a price converts into a percentage and how often each price actually wins. For why a Classic generally costs less to bet in than the handicap after it, which race at the St Leger costs the most measures the charge race by race across the card.

Every figure on this page is read live from the published record and moves when the record moves.

Common questions

Does the model pick the favourite?

Usually not. Its top-rated runner is more often a horse further down the market, which is a consequence of it spreading chance more evenly across a field than the market does rather than a judgement that the favourite is wrong.

If the model disagrees with the market, who is right?

The market, more often. Over 9,568 races its Brier score is 0.091 against the model's 0.100, and lower is sharper.

Should I back the horses the model rates higher than the market?

No. Backing the model's top pick flat at starting price across every race it has called returns −14.0%, and the wide disagreements sit on the runners the model knows least about.

What does the vs Market column actually mean?

The difference in percentage points between the model's estimated chance and the chance implied by the starting price once the bookmaker's charge is removed. It is a gap between two opinions and carries no claim that either is correct.

Are the cards published before the race?

Yes. Estimates are generated each morning at 09:00 BST from the declared field, and the card labels itself a pre-race estimate once the off time has passed. Nothing is added or amended after a result.

Do you tip the St Leger?

No. Everything in the Lab is published research, the losing figures included, and there is nothing to subscribe to.

A word on all of this

None of this describes a way to win, and no approach we have tested across 29,286 races has made money. If your betting has stopped being fun, BeGambleAware has free, confidential help and the National Gambling Helpline is on 0808 8020 133. 18+.