Affect of bets on final BSP

[Trickie13]

Hi Everyone

I know this isn't really the "right" place to post this - apologies for that - but it's probably the one place where I might get an intelligent response from someone who has enough of a "feel" for the markets to be able to answer my query. What I would like to get a rough idea of is, to what extent my bet at Betfair SP will affect the final SP.

I do realise there can be no precise answer to this. It depends on the size of the market and of course the selection itself. But let's suppose I am betting in ten random races per day, in the place market, and I want to place bets on horses who currently have Betfair place SP odds between say 1.4 and 4.0, with most being between 1.8 and 2.5. To what extent, on average, is my £100 bet likely to decrease the final SP? What about a £1000 bet? Would the final price be likely to fall by 0.1, 0.2, 0.5? Would it make a difference placing the bet half an hour before racing starts or placing the bet later (i.e. would an earlier bet discourage others from betting at BSP?) Knowing this, or at least having a rough idea, would be very important for what I am currently working on.

As far as I can tell, there is no way that I can actually calculate any of this for myself. I can see that neither the "Near" nor the "Far" prices are actually accurate. So I'm asking if someone who has a good general feel for the market can give me a good idea what to expect - or if you can advise me where else would be the best place to post this question.

Many thanks

Rich

[marfius]

Hi Rich,

I have the exact same question - did you ever figure out the answer or find any good material on this?

Thanks,
Matt

[only1jake]

From what I've seen with my bets is that there are many factors. It just depends what side your bet is on, how much it is and what current bets are in the market.

Say you want to back at BSP for 500 and its almost about to go in play... The market reads 4.4 on back side with the top price showing 100 on it and lay side shows 4.6 with 400... This seems like you would have to eat through the 4.40 and take lower prices because your bet of 500 is larger than whats available, however there could be someone trying to lay this runner for 1k at whatever the BSP is, so you are likely to get an even better price than 4.4 because of this extra bet waiting to lay at BSP...

There's just so many factors to consider how much it will affect the price, almost too hard to tell because you dont really know how much is available at the inplay moment.

[marfius]

I've been looking at some of the historical data here http://www.betfairpromo.com/betfairsp/prices/ to get an idea of the sort of volumes and prices that are going through some of the different race courses / races / horses. It gives the PPTRADEDVOL (amount traded before the off) and PPWAP (weighted average price), but it doesn't give any indication of how much was left unmatched and on which side the excess was (eg were there a ton of people trying to back that didn't get eaten, or vice versa).

And there's no indication of what the volume was that went into creating the BSP. If I could see that the BSP was made up of £10m backers stakes, then I'd have no issue putting £1k on and not shifting the odds. If the BSP is made up of £5k backers stakes, then clearly sticking an extra £1k on is going to noticeably shift the BSP. Any idea where I might be able to find any of this information?

Thanks!
Matt

[only1jake]

I haven't used any historical data before so I couldn't say where you could find any more! But from what I've seen the only real way to tell would be to log the market up until inplay(which would give you the bets in the market) and then once into play, you'll be able to see the BSP and the Backers' Stake and Layers' Liability for BSP.(which would give you an idea of the general volumes)

I dont think there is any historic data on these stakes other than just what the market volume was and runner BSP. So I see the only way of knowing this would be to log the data or watch the markets yourself

[marfius]

Hi Jake,

Thanks so far for your help, really appreciate it!

How would you go about logging the backers stake and layers liability? Do you have to screen scrape it off the website? I've been trying to get this data via the API but have had no luck, the "backStakeTaken" and "layLiabilityTaken" always seem to come back blank for me, so I'm guessing these fields are specific to my own bets (aka how much of my BSP bet went into the BSP) and not the actual market volumes. When I click on the little graph icon next to a horse on the exchange website though I can see these values, but if I can get them via the API that would be much cleaner than trying to scrape the HTML table

It's a shame those numbers aren't included in the historical files, would be really useful!

Cheers,
Matt

[only1jake]

Yep those are the numbers youre after! However I'm not sure those are the actual parameters you can get data on. If you send off a ListMarketBook with PriceProjection and PriceData for SP_AVAILABLE or SP_TRADED would that return what you're looking for before/after race start? It shows those as being:

PriceData

SP_AVAILABLE - Amount available for the BSP auction.
SP_TRADED - Amount traded in the BSP auction.

So I think those would be returned for each runner in the runner list? I haven't tested this but just had a good look for it!

Something like this:

"{""jsonrpc"": ""2.0"",""method"": ""SportsAPING/v1.0/listMarketBook"",""params"": {""marketIds"": [""" & marketid & """], ""priceProjection"": { ""priceData"": [""SP_TRADED""] }}, ""id"": 1}"

[marfius]

Hi Jake,

You are exactly right, and that was the API call I was trying but was never getting any data back (just blank values for the 'backStakeTaken' and 'layLiabilityTaken') so I sent off a message to Betfair Support and it turns out it's because I'm using the Delayed API key, and that data only gets populated when you have a non-Delayed API key. So I just need to sort that out and I should be able to start collecting that data for myself! (Just wanted to post that here in case anyone else comes looking with the same question )

Thanks for all your help on this, much appreciated - and happy betting!

Cheers,
Matt

[LiamP]

You can see this data in the historical data although you will have to pay.