Calculating Value

[YorkshireFootyFan]

If laying football teams what criteria do you use. At the moment I'm using a strict mathematical criteria but it doesn't seem right, and i'm not entirely comfortable with some of the lays recommended. Before laying I look for a 10% margin on my 100% price, so for a 2.0 shot I'll lay it at 50% +5%, so 1.81 or less. That's fine and i'm happy with that. However if a team comes out at 10.0 to 100% on my figures, then i'll lay it at 9.0 (10%+1%) - this though seems to make it very easy to lay the longer priced aways compared the home price aways, i'm just uneasy laying such long shots on what mathematically is 10% but is only a small price move. I'm in the process of back testing to see how accurate the ratings are over the range of prices, just thought i'd ask to see if anyone else has any views here.

[Gingertipster]

YFF, If you are laying , why not do it the way a bookie makes his book? Don't know what over-round bookies work to in football. Say a bookie believes: Team A has a 62% chance True 8/13, he might add 3% (62+3= 65%) to offer 8/15 The Draw might be 28% True 5/2, adding 3% (28+3= 31%) to offer 9/4 Team B has a 10% True 9/1, adding 2.5% (10+2.5= 12.5%) to offer 7/1 So you could work in the same way in any game (not this one). Although I'd have a greater "margin for error". Anything you believe has a 62% true 8/13 chance you could lay at shorter than 8/15 Anything you believe has a true 28% 5/2 chance you could lay at shorter than 9/4 Anything you make a 10% chance lay it at shorter than 7/1. Depending how confident you are YFF with your 100% book, you will probably need a sliding scale of margin for error. Something like a bigger difference than: 5% odds-on shots, 4% Evens to 2/1, 3.5% 85/40 to 100/30, 3% 7/2 to 7/1, 2.5% 15/2 to 15/1, 2% 16/1 to 33/1, 1.5% 40/1 to 100/1. Laying something you believe has a true 9/1 chance (10.00) at 8/1 (9.00) means you're laying something that in your own opinion is just 1% difference to your 100% tissue (11% = 8/1 and 10% = 9/1, just 1% difference) . Not even a bookmaker with the best odds compiler adds just 1% at those prices. Different if we were talking something he considers a 0.5% chance (true 200/1 shot) offered at 66/1 (1.5%).

[YorkshireFootyFan]

Re: Calculating Value An interesting and appreciated reply GT. I'm in a position to grade my lays by the percentage of value they generate, so I'll be able to see if the P+L improves as the margin improves, as you suggest it might and as you'd hope if the prices i'm compiling are any good.

[Gingertipster]

Re: Calculating Value It's always best to have a certain degree of margin for error. Betting on something that is 9/1 when your 100% book says it should be 8/1; only gives you a margin for error of 1% (10% for 9/1 and 11% for 8/1). Even the best professional gamblers aren't good enough to sustain a profit with just 1% margin for error. :ok

[Sir ratholer]

Re: Calculating Value Great post GT. I've learnt a lot from reading that as well, and will be applying that to my system similarly. It was definitely something I wasn't happy with myself as I've never worked in the betting industry and didn't really know how a bookie would calculate their profit margins. Makes total sense now, thanks.

[v-zero]

Re: Calculating Value Convert your lay odds to equivalent back odds, and multiply by the probability of winning. Any number >1 represents 'value'... take away one from your number to get percentage edge.