I've been watching some pre-race markets recently in between trying some other things and I noticed a particular repeating behaviour on one type of market only. For some bizarre reason I only seem to be able to exploit it with small stakes (under £100 optimal success is between £10 - £20). I obviously don't want to give away too much but it centres around only ever backing a favourite at different prices depending on a set of conditions I've observed.
Why would the stake size render this as -EV?
Tiny Edge in Only One Market Type
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ShaunWhite
- Posts: 10469
- Joined: Sat Sep 03, 2016 3:42 am
Hope you don't mind a lazy reply.... I gave my opinion to gpt and it's re-worded it for me...
Most likely, the edge you're exploiting is being created by retail flow or "dumb money", and there's only so much of that available before it's soaked up. When you're staking £20–£50, you're small enough to feed off that flow without disrupting it. But as soon as you scale up, you're either:
competing with others who are sharper and faster than you, or
placing size that influences the very pattern you're trying to exploit.
In that sense, the edge isn’t inherently -EV at larger stakes—it just can’t absorb more money without collapsing or attracting competition. That's often the case with microstructure inefficiencies: profitable at small scale, self-defeating at size.
Most likely, the edge you're exploiting is being created by retail flow or "dumb money", and there's only so much of that available before it's soaked up. When you're staking £20–£50, you're small enough to feed off that flow without disrupting it. But as soon as you scale up, you're either:
competing with others who are sharper and faster than you, or
placing size that influences the very pattern you're trying to exploit.
In that sense, the edge isn’t inherently -EV at larger stakes—it just can’t absorb more money without collapsing or attracting competition. That's often the case with microstructure inefficiencies: profitable at small scale, self-defeating at size.
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TupleVision
- Posts: 84
- Joined: Wed Feb 12, 2025 12:19 pm
Makes sense I guess. I'll stick with it as it's working nicely at the moment, maybe in time I'll simply spot other opportunities to add to the basket perhaps.
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jamesedwards
- Posts: 4042
- Joined: Wed Nov 21, 2018 6:16 pm
The greater your stake the lower your EV. This is because as your stake increases the time/risk involved in matching will increase along with it.
Taking it to extremes, imagine wanting to back over 2.5 goals in-play at current market price of 2.0 for £1. You will match the full amount easily. Now try backing over 2.5 goals at that price for £1m. It would take many minutes to get the full amount matched during which the true odds would be growing while you're trying to get your 2.0 matched. Your EV% will be dropping like a stone as time passes.
Depending on your strategy the impact of stake may hardly be noticeable, or it might swing wildly from profit to loss with just small increases. Time to dust off this graph from a greyhound automation of mine from few years back.
Taking it to extremes, imagine wanting to back over 2.5 goals in-play at current market price of 2.0 for £1. You will match the full amount easily. Now try backing over 2.5 goals at that price for £1m. It would take many minutes to get the full amount matched during which the true odds would be growing while you're trying to get your 2.0 matched. Your EV% will be dropping like a stone as time passes.
Depending on your strategy the impact of stake may hardly be noticeable, or it might swing wildly from profit to loss with just small increases. Time to dust off this graph from a greyhound automation of mine from few years back.
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ShaunWhite
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Tricky though, it's tempting to keep tinkering when the answer is to bank it as is and move on. Finding that first small thing that pays for you to keep looking for something bigger is a bit of a milestone.TupleVision wrote: ↑Sun Jul 13, 2025 6:02 pmMakes sense I guess. I'll stick with it as it's working nicely at the moment, maybe in time I'll simply spot other opportunities to add to the basket perhaps.
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TupleVision
- Posts: 84
- Joined: Wed Feb 12, 2025 12:19 pm
Thanks both for the replies. This is really the first thing that's actually looked promising long term. Its certainly not a full time job replacement but £20 a day or so for what amounts to a few mins work on a handful of races seems worth it 
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ShaunWhite
- Posts: 10469
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Don't knock it. £20 a day is over 7 grand a year tax free. Some people have to flip burgers for 700 hrs for that.