Betfair cross matching explained!

News, chat and debate about the Betfair betting exchange.
steven1976
Posts: 1744
Joined: Tue Jan 19, 2010 6:28 am

I think it's easiest to see on 1.01 on horse races dallas. If you watch closely sometimes you will see say 2-4k waiting on the lay side and then all of a sudden 22k is matched. I imagine this will be explained as a refresh issue but it should be reasonably easy to see.
User avatar
Euler
Posts: 24701
Joined: Wed Nov 10, 2010 1:39 pm
Location: Bet Angel HQ

If anybody want's to give me clear and specific detail on anything that think that doesn't look right I'm happy to take it up with Betfair.
quant
Posts: 1
Joined: Wed Dec 02, 2015 8:02 am

LeTiss 4pm wrote:If I back Djokovic for £30 at 1.50, but only £20 is available, the other £10 might come from laying a backer of Federer at 3.00

According to BF my £30 would show £40 matched on Djokovic and £20 Federer, as opposed to what I'd expect to see, which is £60 matched on Djokovic

This doesn't explain though why I can see my bet sat waiting on a selection, and the matched figure for that selection is indicating I should be getting matched, but am not
I'm a bit confused by how matched volume is computed for cross matching.

Say I want to back Djokovic for £10 at 1.50.

Situation 1: There is a layer of Djokovic that matches this, then as I understand it the matched volume on Djokovic goes up by £20.

Situation 2: There are no layers of Djokovic, but instead I'm cross matched to lay a backer of Federer for £5 at 3.00.
How much does the volume on Federer go up in this case? I suppose if I was "originally" a layer here it would go up by £10 (twice backer's stake), but is it now the case that since I'm "originally" a backer of £10, it would go up by £20 (twice "original" backer's stake)?
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

A good visual as to how Cross Matching works..on todays Snooker markets..
Image on the left = No XM, Right Image = XM on..
You do not have the required permissions to view the files attached to this post.
User avatar
LeTiss
Posts: 5386
Joined: Fri May 08, 2009 6:04 pm

2 selections are easy to understand and accept Peter. Where XM starts to become a grey area is when there's 3 + selections, as it becomes unclear as to who is getting matched and why. I don't like that, it makes the matching process look like it's being tampered with
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

Yes I agree..
Also for anyone using automated strategies; you can see how things (EG WOM) is shown differently depending upon whether you have it switched on of off.. so could help or hinder a strategy..
User avatar
LeTiss
Posts: 5386
Joined: Fri May 08, 2009 6:04 pm

PeterLe wrote:Yes I agree..
Also for anyone using automated strategies; you can see how things (EG WOM) is shown differently depending upon whether you have it switched on of off.. so could help or hinder a strategy..
Yeah, that's a great point actually

I've come to realise over the years that WOM is quite often a trap, as much as a guide.
vhdgkl
Posts: 63
Joined: Thu Feb 25, 2016 9:26 am

PeterLe wrote:Cross matching was introduced on the 24th Nov 2010 (?) and I remember the build up wondering what would happen (there is a tread on here somewhere)
This explains what it is and is the best explanation Ive seen:-

https://api.developer.betfair.com/servi ... rtual+Bets

Although its a straight forward calcualtion; it seems to behave differently these days that when introduced originally.

Here is a video I did at the time (Pause the video as it plays and you can compare the subtle differencesin odds/money avail at those odds between one account with Cross Matching and one account with no cross matching)

https://www.youtube.com/watch?v=3njy483sL-w

Once you understand how it works; you will drive yourself mad trying to work out how to exploit it! :D
https://www.youtube.com/watch?v=3njy483sL-w

i saw this link

it's really hard to understand formula..and it's really really hard to undersand why in a moment(13seconds)the lay odds of third is different(4,1no xm-4,2 whit xm :o )
the book percentage is 101.5 for the lay column in that moment(and backers column is under 100percentage!), why the odds up?

ps:I think the key to understanding why the odds when they take you take you systematically disadvantage 'to look for in this cross-matching (english is not my language :D )
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

Folks,
Pre API-NG, Betfair had a doc that explained the cross matching principle, they had a example based on a football match and accompanying it they had a formula.
Does anyone have a copy of that formula please? (betfair still have examples of cross matching but they seem to have removed the formula)
I know betfair cross match against linked markets, I know that, but Im just looking for that original formula, if anyone can help
Thanks in advance
regards
Peter
spreadbetting
Posts: 3140
Joined: Sun Jan 31, 2010 8:06 pm

1 / (N –∑ 1/(best to lay price of other runners))

Where N is the number of winners that market will have, e.g. for a “to win” market N = 1, for a place market with 3 winners N = 3.

For each runner calculate the available stake at that price as:

MIN(odds1*stake1, odds2*stake2...oddsn*staken) / [the price calculated in step a. above]
In plain English the stake you can match is limited by the payout (odds*stake) available on each of
the component bets that you’d need to match.
Last edited by spreadbetting on Wed Jun 27, 2018 7:17 pm, edited 1 time in total.
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

spreadbetting wrote:
Wed Jun 27, 2018 6:55 pm
1 / (N –∑ 1/(best to lay price of other runners))

As far as I can remember.
Hi
Thanks for the reply; (good memory! :D ) Yes I just found it too...Extract below

For the available to back prices on the LHS:
• For each runner calculate the best price at which you could effectively back that runner by
laying all the others:
1 / (N –∑ 1/(best to lay price of other runners))
Where N is the number of winners that market will have, e.g. for a “to win” market N = 1, for a place
market with 3 winners N = 3.
• For each runner calculate the available stake at that price as:
MIN(odds1*stake1, odds2*stake2…oddsn*staken) / [the price calculated in step a. above]
In plain English the stake you can match is limited by the payout (odds*stake) available on each of
the component bets that you’d need to match.
• Repeat from the first step above

Taken from : http://www.bettingdeveloper.org/docs/Be ... 0Guide.pdf
Post Reply

Return to “Betfair exchange”