Accuracy of Betfair SP

The sport of kings.
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Slippery Richie
Posts: 20
Joined: Tue Feb 02, 2016 10:02 pm

Hi,

I've had a quick search on the forums and wasn't able to find much discussion on this.

Is the BSP a true reflection of the probability of an event occurring eg a horse winning in the win markets?

I've always been led to believe that the BSP is reliable, however having recently read/heard some differing opinions I'm now uncertain.

Thoughts?
Group1Buff
Posts: 4
Joined: Wed Feb 06, 2019 10:15 am

Long term yes, it's extremely efficient but on a race by race basis it's not necessarily an accurate representation of the true chances of a horse owing to the way it's calculated. A horse could be trading at a narrow range of say $3.80-$3.90 right before the jump and then SP at $3.50 or $4.30 due to the way it is calculated. This is particularly true in less liquid markets (AU and US racing for example) where a large SP bet placed on either side will significantly shift the market. By and large though it's the most accurate metric most will have access to.
spreadbetting
Posts: 3140
Joined: Sun Jan 31, 2010 8:06 pm

Just ran a quick query on my database - out of 1,308,149 runners the winning BSP's added up to 1,287,046 so that's around 98.4% accurate over 268,444 races.
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