How do the odds move?

[Derek27]

Apologies to the OP - I seem to have got his comments cross-matched with CallumPerry's.

[spreadbetting]

Thank you, I did not know such documentation existed.

No problem , there's a thread explaining things here and the last post has a link to Betfair's document about the calculation

viewtopic.php?f=15&t=11066

Page 24
http://www.bettingdeveloper.org/docs/Be ... 0Guide.pdf

[Derek27]

Thanks SB, this is something I never knew.

The exchange itself matches and processes bets on a ~200ms cycle and any changes are pushed to the
delta caches. This means, of cou
rse, that if you request pricin
g data less than 200ms after a previous
change, you cannot possibly get a
different response as the exc
hange would not have completed a bet
processing cycle.

What a pain in the bum, you'd think Adobe would have made copy and pasting easier!

The exchange itself matches and processes bets on a ~200ms cycle and any changes are pushed to the delta caches. This means, of course, that if you request pricing data less than 200ms after a previous change, you cannot possibly get a different response as the exchange would not have completed a bet processing cycle.

[Euler]

I've often seen people obsess about getting in the fast ping, but Betfair has been 200ms for a long time negating the benefit of high speed. An arms race developed early on when Betfair didn't cache and Betfair decided to change the way the exchange worked to stop that ever happening again and allow them to control the expense side of the equation in terms of how the exchange works. Loads of stuff failed when they did this, but XM has ruined a lot of strategies as well.

[sriel1]

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.

[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