What happens to a combination when one of its legs is void
A leg can fail to happen for reasons that are nobody's fault: a player does not start, a market is settled on a correction, an event is abandoned. The combination is then repaired, and the repair is where a reader is most likely to be paid a different number from the one they expect.
- four legs, multiplied
- 13.44
- four legs, composed
- 10.80
- the void leg
- 2.40
- the repair error
- 6.7%
When a leg of a composed bet is void, the combination is re-priced from its remaining legs rather than divided by the void leg's price. Sample D shows the difference: a 10.80 combination divided by a void leg of 2.40 gives 4.50, while the real three-leg combination prices at 4.80 - a 6.7% gap, worth 3.00 on a 10.00 stake, and 9 of 40 terms pages state the rule.
Why dividing is the natural mistake
The arithmetic of a product is reversible: if 5.60 was reached by multiplying 1.60, 1.75 and 2.00, then removing one leg is attained by dividing. That works for a printed accumulator, where the price is exactly the product. It fails for a composed market, because the composed price was never the product. Removing a leg removes its contribution to the product, but the remaining legs still have the correlation between them, and the correlation has to be re-estimated for the smaller set rather than inferred from the larger one.
What the samples show
| Figure | Price | Return on 10.00 | How it was produced |
|---|---|---|---|
| The four legs multiplied | 13.44 | 134.40 | 1.60 x 1.75 x 2.00 x 2.40 |
| The combination as composed | 10.80 | 108.00 | The model's joint chance of all four |
| The repair by division | 4.50 | 45.00 | 10.80 divided by the void leg, 2.40 |
| The repair by re-pricing | 4.80 | 48.00 | The real three-leg combination price |
| What the two repairs differ by | 0.30 | 3.00 | 6.7% of the divided figure |
When the repair changes the bet
Two edge cases are worth knowing about before they happen. If the void leg is the one the customer cared about - the named player's shots, the goals market - the combination that survives is not the bet they placed, and a reader who would not have made the smaller bet may prefer the whole stake returned. And if several legs of one combination are settled on the same corrected statistic, a single correction can void more than one leg, which changes the remaining set twice. Neither case is covered by the division method at all.
- Whether the terms state that the combination is re-priced from its remaining legs, or say nothing.
- Whether the re-pricing uses the price that existed before the void or the model as it stands after.
- Whether a combination with one leg left is still a combination or becomes a single bet at that leg's price.
- Whether the void leg's stake is returned in cash, retained in the combination, or simply removed.
- Whether a correction to a statistic can void more than one leg of the same combination at once.