Reduction factor

[Dices]

Hi, Does anyone knows what formula is been used to calculate the reduction factor at races? Thanks

[Dices]

Re: Reduction factor Found this:

Rule 4 will not apply if the horse which was withdrawn was at odds of above about 14-1. Many bookmakers do not apply rule 4 above odds of 9-1 (10.0). Rule 4 will only affect you if your horse wins the race. If it loses the bet behaves normally. The size of the rule 4 deduction depends on the odds of the horse which was withdrawn at the time of its withdrawal. The following scale is copied from Sean Graham's T&Cs: **** Late Withdrawals Where a horse is withdrawn before coming under Starter's orders, or is officially deemed by the Starter to have taken no part in the race, stakes will be returned on the withdrawn horse and winning bets will be subject to deductions in accordance with Tattersalls' Rule 4©. The rate of deduction will be based on the following scale:- Current price at withdrawal Deductions in the pound. 3/10 or lower £0.75 3/0 to 2/5 £0.70 2/5 to 8/15 £0.65 8/15 to 8/13 £0.60 8/13 to 4/5 £0.55 4/5 to 20/21 £0.50 20/21 to 6/5 £0.45 6/5 to 6/4 £0.40 6/4 to 7/4 £0.35 7/4 to 9/4 £0.30 9/4 to 3/1 £0.25 3/1 to 4/1 £0.20 4/1 to 11/2 £0.15 11/2 to 9/1 £0.10 9/1 to 14/1 £0.05 15/1 and higher no deductions made In the event of two or more horses being withdrawn before coming under Starter's orders, the total deductions shall not exceed £0.75 in £. Should a horse be withdrawn and a new market formed, then any bets laid at 'Show' prices prior to the new show will be subject to the above deductions. In the event of a further withdrawal after the market has been re-formed, bets placed at 'Show' prices in the original market will be subject to a further deduction based on the price of the withdrawn horse in the original market. Bets placed in the new market will be subject to a deduction based on the current price. **** In fact Sean Graham do not deduct the 5% rule 4. Many bookmakers leave their early price odds unchanged after a withdrawal and apply rule 4. Once the market starts to move in ernest nearer the "off" the prices will have been adjusted and rule 4 will probably not apply. (I would not advise attempting to bet within 1/2 an hour of the start of a race unless you are very experienced.) Betfair do not use the same scale, but give each horse a "deduction factor". If there is a non-runner the time of withdrawal and the deduction factor are listed under the "rules" tab on the right hand side. The market is suspended on the announcement of a non-runner and re-formed straight away. Any bets placed after this are not subject to a deduction. DANGER - if you find a race which appears to contain more than one arb, check very carefully that you are not comparing bookies prices before rule 4 with the re-formed market at Betfair. Matching under these circumstances can be VERY expensive if your horse wins. Some bookmakers (Sean Graham is one) warn you that a rule 4 deduction may apply. If so, it doesn't necessarily mean you can't bet on the race. First check what the odds of the withdrawn horse were. If it was say 20 then you can safely ignore it. How to calculate the revised odds after rule 4 Rule 4 applies only to the winnings, not to the stake. Suppose your horse is quoted at 4.0 and the rule 4 deduction is 20%. The revised odds are: 4 minus 1 (to remove the stake) = 3 minus 20% of 3 (0.6) = 2.4 plus 1 (to return it to proper decimal odds including the stake) = 3.4. Therefore if you found an arb at the bookies which was 4.0/2.8 it would still be an arb, but 4.0/3.4 would not. The difficulty with rule 4 is that as the odds of the withdrawn horse are likely to be different at Betfair than at the bookies there can be quite a difference in the size of the deduction. It is likely to be smaller at Betfair because the odds are likely to be longer, so your lay risk will shrink less than your winnings. This can play havoc with the matching process and cost you money. However, in practise I find this effect is rare as your horse has to win first. The danger of betting on different markets as outlined above is potentially much more costly.

and this:

, Betfair apply the same percentages deductions to their bets. However it should be noted that they are applied to the higher (digital odds price) so in actual price terms the deductions are larger. For example.

You have bet £100 on a horse at 8-1 and a withdrawn horse causes a 25p rule 4. Your horse wins.

At a bookmaker your 8/1 will be reduced to 6/1 (25% of 8) and your return will be £600 plus your stake

At Betfair your 8/1 (9.0 digital odds) will be reduced to 5.75 to 1 ( 25% of 9.0 ) and your return would be £575 plus your stake (less commission)

In reality, it maybe that the odds you managed to match at on Betfair were higher than the 8/1 you would have got at a bookmaker and therefore you may still be advantaged to bet with Betfair, but you should be aware of the difference in the deduction rule.