Bookmaker over-rounds for over/unders markets

[LFCBADBOY]

Hi guys,

Does anybody have an idea of the approximate % over-round bookmakers work off for their overs/unders markets.

Someone suggested to me it is about 10%, could anyone confirm this?

Thanks in advance

[devomark2]

celtic tonight is over 2.5 @1.61 and unders is 2.25 overall odds is 0.94 so your underound is 6%,inverness tonight is 2.00 and 1.80 overall odds is 0.95,so its 5% loss for the punter if he dutched both outcomes on this one,so the bookies overound is 5-6%,these are bet 365 odds.

[LFCBADBOY]

Thanks very much for that reply devomark.

I guess what I want to know is whether the odds are skewed by the bookmaker to either side.

I.e over/under 1.5 is say 1.25 and 4.25 respectively. Which side does the bookie build most margin into? And how much would that be? i.e. should 1.25 really be 1.35, or would 1.3 be a fair analysis of the true odds?

[Wednesday 13]

Thanks very much for that reply devomark.

I guess what I want to know is whether the odds are skewed by the bookmaker to either side.

I.e over/under 1.5 is say 1.25 and 4.25 respectively. Which side does the bookie build most margin into? And how much would that be? i.e. should 1.25 really be 1.35, or would 1.3 be a fair analysis of the true odds?

Errrrrrm... incidentally, there was quite similar question this morning over there at Punters Lounge; I hope it's not against rules of this forum if I copy/paste my opinion from there, in order not to type again:

I can't give you reliable answer, but here is my opinion: I believe that, for "accurate estimation" of true odds (i.e., odds bookmaker found to be true according to his analysis, before applying overround), you must look both sides of the same market (over 1.5 and under 1.5, just because of the overround), rather than the same side of different markets (over 1.5 and over 3.5).

Namely, in two-runners markets where both runners are at similar prices (over/under 2.5, for example), overround is pretty equally distributed between runners; but in markets where one runner has significantly higher odds than another (and it's case with over/under 1.5), I believe that bookies include more of their margin into higher priced runner; they do it to protect themselves from worst case scenario, i.e., to decrease their liability if runner at high odds wins.

Let me try to explain on a example; I have recently analyzed overround of over/under 2.5 odds offered by local bookie here, and found it way too high - 12 to 15 %; if I assume the same margin for over/under 1.5 (don't have time now to go to some odds comparison and check it), that means odds of 1.22 for over 1.5 imply odds of around 3.10 for under 1.5, i.e., probabilities of around 82% and 32% (-> 114%); now, I believe that bookie allocated more of those 14% in under 1.5 odds, so I'd go with, roughly said, (82-5) = 77% and (32-9) = 23%, which gives you "fair" odds, as calculated by bookmaker, of around 1.30 and 4.35.

Now you may understand why bookie distributed it unevenly: if he allocated equal margin, around 7 %, to both runners, he would have (77+7) = 84% and (23+7) = 30%, which gives odds of around 1.19 and 3.33, instead of 1.22 and 3.10 that he offered in our example - so he would improve his liability for only 3 units on overs, but would lose 23 units more on unders.

As I said, this is just my opinion, so please take it with reserve.

[LFCBADBOY]

ha ha, that's because I am the same person

[devomark2]

i just do a few stats check on a game and if say 1.33 was being offered on over 1.5 and i work out the true odds should be say 1.25 then i know i am getting value,but the book has got to be tighter on the fav outcome as more punters are on the fav,im no expert but i look for what i think is good value in any given market and try to keep things as simple as poss,anyway Lfc i hope you were on overs the other night with your lot against fulham,under 2.5 was fav as far as i remember,so good value on that one.

[LFCBADBOY]

Devomark, I also do the same thing, but just want to compare my "true odds" values I am getting to what the bookies actually consider the true odds to be, so just trying to reengineer their odds really.

I had over 1.5 in the fulham game, I think it was the quickest over 1.5 I have ever won (6 mins i think it took)! Just a shame KK wasn't made manager at the beginning of the season!

[Wednesday 13]

ha ha, that's because I am the same person

Didn't guess it! And I thought to myself how it was strange to have two people looking for the same thing the same day... Sorry for doubling up the answers.

[devomark2]

Devomark, I also do the same thing, but just want to compare my "true odds" values I am getting to what the bookies actually consider the true odds to be, so just trying to reengineer their odds really.

I had over 1.5 in the fulham game, I think it was the quickest over 1.5 I have ever won (6 mins i think it took)! Just a shame KK wasn't made manager at the beginning of the season!

yeah king kenny is the nuts mate,was one of my fav players back in the day,and thats coming from a gooner!anyway all the best in your scheming