In the article about odds movement, we saw that if we are laying horses to lose, we should concentrate on those horses whose odds increase and avoid those whose odds decrease in the last five minutes of betting.

If we are backing horses to win, we should concentrate on those horses whose odds decrease and avoid those whose odds increase in the last five minutes of betting.

In the previous article, we also learned that there are two exceptions to this rule: Steamers and Drifters.

Firstly, let’s cover Steamers.

A Steamer is defined as horse whose implied percentage chance of winning increases by 5%, or more, in the last two hours of betting.

To calculate the Implied Percentage Chance of winning, we simply add ‘1’ to the fractional odds and divide the results into 100.

By way of an example:

If the odds are 9/1, the Implied Percentage Chance of winning = 100/(9 + 1) = 100/10 = 10%.

If the implied percentage chance of winning of our selection increases from 10% by 5% to 15% in the last two hours of betting, then it is classified as a Steamer.

To calculate the odds if the implied percentage chance of winning is 15%, we simply divided 100 by the implied percentage chance of winning and then subtract 1.

So, 100/15 = 6.67. 6.67 - 1 = 5.67.

So, an implied percentage chance of winning of 15% corresponds to fractional odds of approximately 5.67/1.

This is approximately equal to fractional odds of 11/2.

Therefore, for a horse, whose odds are 9/1, to be classified as a Steamer, its odds must fall to 11/2 or lower in the last two hours of betting.

In the previous article, we learned that statistics show that horses whose pre-race odds fall during pre-race betting have a greater chance of winning than their odds imply.

We also learned that there is an exception to this rule. The exception is Steamers.

If a horse is classified as a Steamer, then statistics show that it wins less frequently than its odds imply and that a profit can be made by laying Steamers to lose.

The rule, therefore, becomes: When backing horses to win, concentrate on horses whose pre-race odds shorten unless it can be classified as a steamer.

Now, let’s look at Drifters.

A Drifter is defined as horse whose implied percentage chance of winning decreases by 5%, or more, in the last two hours of betting.

To calculate the Implied Percentage Chance of winning, we simply add ‘1’ to the fractional odds and divide the results into 100.

By way of an example: If the odds are 9/1, the Implied Percentage Chance of winning = 100/(9 + 1) = 100/10 = 10%.

If the implied percentage chance of winning of a selection decreases from 10% by 5% to 5% in the last two hours of betting, then it is classified as a Drifter.

To calculate the odds if the implied percentage chance of winning are 5%, we simply divided 100 by the implied percentage chance of winning and then subtract 1.

So, 100/5 = 20. 20 - 1 = 19.

So, an implied percentage chance of winning of 5% corresponds to odds of 19/1.

Therefore, for a horse, whose odds are 9/1, to be classified as a Drifter, its odds must increase to 19/1 or higher in the last two hours of betting.

In the previous article, we learned that statistics show that horses whose odds increase in the pre-race betting have a lesser chance of winning than their odds imply.

We also learned that there is an exception to this rule.

The one exception to this rule is Drifters.

If a horse is classified as a Drifter, then statistics show that it wins more frequently than its odds imply and that a profit can be made by backing Drifters to win.

The rule, therefore, becomes: When laying horses to lose, concentrate on horses whose pre-race odds lengthen unless it can be classified as a Drifter.

Just in case the above causes some confusion, please find a table below which summarises the above:

We have now seen that if a selection’s odds increase in pre-race betting, then we should lay it to lose unless it can be classified as a drifter.

We have also seen that if a selection’s odds decrease in pre-race betting, we should back it to win unless it can be classified as a steamer.