How do the odds move?

[Derek27]

From what I understand, if a backed a horse for £200 and there is only £100 in lay bets waiting to be filled at that price, then Betfair will place lay bets on the other horses so that the other £100 will be absorbed into the market and the over round will adjust to nearly 100% again.

Only the the overall price is as good or better than the price you're backing at. It only happens in markets with a tight overround or when somebody takes a price well away from current prices.

[Dallas]

Thanks everyone. After reading through the comments on this thread and doing a bit of homework I'm clearly looking to understand how crossmatching works.

From what I understand, if a backed a horse for £200 and there is only £100 in lay bets waiting to be filled at that price, then Betfair will place lay bets on the other horses so that the other £100 will be absorbed into the market and the over round will adjust to nearly 100% again.

I'm starting to visualise how this works for a 2 runner race, it seems a lot more complex when there are several other runners in the race and which horse Betfair will place the lay bets on.

Two runner markets are certainly easier to see it on, these couple of videos might help
https://www.youtube.com/watch?v=bJIXvCQ3ieU
https://www.youtube.com/watch?v=Bys1lu-18wo

[spreadbetting]

I'm starting to visualise how this works for a 2 runner race, it seems a lot more complex when there are several other runners in the race and which horse Betfair will place the lay bets on.

The liability gets spread equally over all the other runners in the market until it's either all gone or the other runners odds don't create an overround book. Once a price point has been used up they use the next price point and stakes to calculate the x-match odds.

Page 24 onwards from the Betfair docs probably explains how x-matching operates better than I can, http://www.bettingdeveloper.org/docs/Be ... 0Guide.pdf